LNIS V005 August 31, 2023 1

LunaNet Interoperability 

Specification Document

Draft Version 5
LNIS V005 August 31, 2023 2

1 TABLE OF CONTENTS

1 Introduction 14

1.1 Purpose .......................................................................................................................................... 14

1.2 Scope.............................................................................................................................................. 15

1.3 Security Considerations................................................................................................................. 15

1.4 Applicable Documents................................................................................................................... 16

2 LunaNet Interoperability Overview ....................................................................................................... 17

3 User Services.......................................................................................................................................... 21

3.1 Communications Services.............................................................................................................. 21

3.1.1 Real-Time Communications Services...................................................................................................22

3.1.2 Store-and-Forward Communications Services ....................................................................................23

3.2 Position, Navigation, and Timing Services..................................................................................... 23

3.2.1 Reference Signals.................................................................................................................................25

3.2.2 Lunar Augmented Navigation System (LANS)......................................................................................26

3.2.3 One-Way Measurements.....................................................................................................................29

3.2.4 Two-Way Measurements.....................................................................................................................30

3.2.5 Two-Way Transponder ........................................................................................................................30

3.2.6 Supplemental Navigation Products .....................................................................................................31

3.2.7 Location Service...................................................................................................................................32

3.3 Messaging Services........................................................................................................................ 33

3.4 Detection and Information Services.............................................................................................. 34

3.4.1 Lunar Search and Rescue Services.......................................................................................................35

3.4.2 Space Weather Alerting Services.........................................................................................................37

3.5 Science Services............................................................................................................................. 37

3.6 Service Access................................................................................................................................ 38

3.6.1 Earth-based Scheduling Service...........................................................................................................39

3.6.2 User Initiated Services .........................................................................................................................39

3.6.3 Single Access Links...............................................................................................................................39

3.6.4 Spread Spectrum Links.........................................................................................................................40

3.6.5 Link Establishment...............................................................................................................................41

3.7 Service Combined Capabilities and Inter-relationships................................................................. 43

4 LunaNet Service Provider to User Interfaces......................................................................................... 44

4.1 LNSP-User Lunar Surface Interfaces .............................................................................................. 45

4.2 LNSP-User Proximity Interfaces..................................................................................................... 46

4.3 LNSP-User DWE Interfaces............................................................................................................. 48

4.4 LNSP-User Contingency Interfaces ................................................................................................ 49

4.5 LNSP-User Terrestrial Interfaces.................................................................................................... 50

5 LunaNet Service Provider to LunaNet Service Provider Services........................................................... 51

5.1 LNSP A-LNSP B Communications Services ..................................................................................... 51

5.2 LNSP A-LNSP B PNT Services.......................................................................................................... 51

6 LunaNet Service Provider to LunaNet Service Provider Interfaces........................................................ 52

6.1 LNSP A-LNSP B Lunar Surface Interfaces ....................................................................................... 52

6.2 LNSP A-LNSP B Crosslink Interfaces............................................................................................... 52

6.3 LNSP A-LNSP B DWE Interfaces...................................................................................................... 53

6.4 LNSP A-LNSP B Terrestrial Interfaces............................................................................................. 53
LNIS V005 August 31, 2023 3

7 References and Appendices................................................................................................................... 54

Appendix A Acronyms.......................................................................................................................... 56

Appendix B Signal interface Descriptions ............................................................................................ 58

B.i LNSP-User Proximity Interfaces..................................................................................................... 58

B.i.i Single Access LNSP-User Proximity Interfaces.....................................................................................58

B.i.ii Spread Spectrum LNSP-User Proximity Interfaces...............................................................................69

B.ii LNSP – User DWE Interfaces.......................................................................................................... 72

B.iii LNSP-User Contingency Interfaces ................................................................................................ 80

Appendix C Navigation Parameters..................................................................................................... 86

Appendix D LunaNet Messages............................................................................................................ 89

D.i Overview of Messages................................................................................................................... 89
LNIS V005 August 31, 2023 4

TABLES OF FIGURES

Figure 1: LunaNet Segments ......................................................................................................................17

Figure 2: LunaNet Standard Services and Interfaces between LNSPs and Users......................................18

Figure 3: LunaNet Service Providers Interfaces........................................................................................19

Figure 4: Two Types of Communications Services.....................................................................................21

Figure 5: User Application Simplified Protocol Stack ...............................................................................21

Figure 6: PNT Services Provided by LNSP................................................................................................25

Figure 7: Reference PNT Signals Provided by an LNSP Node ..................................................................26

Figure 8: LANS PNT Concept Provided by LunaNet Nodes ......................................................................27

Figure 9: LANS Full Service Coverage and Performance Volume ............................................................28

Figure 10: Notional LANS South Pole Service Coverage and Performance Volume ................................28

Figure 11: One-Way Measurements Performed by a LNSP Node..............................................................29

Figure 12: Two-Way Measurements Performed by LNSP Node ................................................................30

Figure 13: Two-Way LNSP Node Transponder..........................................................................................31

Figure 14: LNSP Node and user exchange messages using messaging services .......................................33

Figure 15: LunaSAR Data Path Concept of Operations ............................................................................36

Figure 16: LunaNet Scheduling Interfaces Overview.................................................................................38

Figure 17: Augmented Forward Signal Service Provided by a Single LNSP Source.................................41

Figure 18: LunaNet Interoperability Frequency Plan................................................................................44

TABLE OF TABLES

Table 1: Lunar Network Service Provider Interfaces.................................................................................19

Table 2: IP Service Interfaces.....................................................................................................................22

Table 3: Bundle Protocol Service Interfaces..............................................................................................23

Table 4: Message ID and Titles..................................................................................................................34

Table 5: Detection and Information Services.............................................................................................35

Table 6: LNSP–User Lunar Surface-Surface Link Layer Service Interfaces..............................................45

Table 7: LNSP-User Proximity Interfaces Single Access...........................................................................46

Table 8: LNSP-User Proximity Interfaces Spread Spectrum......................................................................47

Table 9: LNSP-User DWE signal interfaces...............................................................................................48

Table 10: LNSP-User Contingency Mode Signal Interfaces ......................................................................49

Table 11: LNSP–User Terrestrial Link Layer Service Interfaces...............................................................50

Table 12: LNSP–LNSP Crosslink Layer Interfaces4...................................................................................52

APPENDIX TABLES:

Table B-1: PFS1a - Proximity Forward S-Band Data Only.......................................................................60

Table B-2: PFS1b - Proximity Forward S-Band Medium Rate w/ Ranging...............................................60

Table B-3: PFS1c - Proximity Forward S-Band Low Rate w/ Ranging .....................................................61

Table B-4: PFS1d - Proximity Forward S-Band High Rate Data Only......................................................61

Table B-5: PFS1e - Proximity Forward S-Band High Rate w/ Ranging ....................................................62

Table B-6: PRS1a - Proximity Return S-Band Data Only ..........................................................................62

Table B-7: PRS1b - Proximity Return S-Band Medium Rate w/ Ranging ..................................................63

Table B-8: PRS1c - Proximity Return S-Band Low Rate w/ Ranging.........................................................63

Table B-9: PRS1d - Proximity Return S-Band High Rate Data Only.........................................................64
LNIS V005 August 31, 2023 5

Table B-10: PRS1e - Proximity Return S-Band High Rate w/ Ranging......................................................64

Table B-11: PFK1 - Proximity Forward K-band Data Only......................................................................65

Table B-12: PFK2 - Proximity Forward K-band Variable Coding and Modulation .................................65

Table B-13: PFK3 - Proximity Forward K-band High-Rate Data Only ....................................................66

Table B-14: PFK4 - Proximity Forward K-band High-Rate Data w/ Ranging..........................................66

Table B-15: PRK1 - Proximity Return K-band Data Only .........................................................................67

Table B-16: PRK2 - Proximity Return K-band Variable Coding and Modulation.....................................67

Table B-17: PRK3 - Proximity Return K-band High-Rate Data Only........................................................68

Table B-18: PRK4 - Proximity Return K-band High-Rate Data w/ Ranging .............................................68

Table B-19: PFS2 - Proximity Forward S-band Medium Rate w/ Ranging ...............................................70

Table B-20: PRS2 - Proximity Return S-Band Spread Spectrum................................................................70

Table B-21: PFS5 - Proximity Forward S-band Augmented Forward Signal (AFS).................................71

Table B-22: PRS5 - Proximity Return S-Band Multiple Access Return (MAR)..........................................71

Table B-23: XU1 - X-band Uplink Medium Rate w/ Ranging ....................................................................74

Table B-24: XU2 - X-band Uplink High Rate w/ Ranging..........................................................................74

Table B-25: XU3 - X-band Uplink Low Rate w/ Ranging...........................................................................75

Table B-26: XU4 - X-band Uplink High Rate Data Only ...........................................................................75

Table B-27: XD1 - X-band Downlink Medium Rate w/ Ranging................................................................76

Table B-28: XD2 - X-band Downlink High Rate w/ Ranging.....................................................................76

Table B-29: XD3 - X-band Downlink Low Rate w/ Ranging......................................................................77

Table B-30: XD4 - X-band Downlink High Rate Data Only ......................................................................77

Table B-31: KU1 - K-band Uplink High Rate Data Only...........................................................................78

Table B-32: KU2 - K-band Uplink High Data w/ Ranging ........................................................................78

Table B-33: KD1- K-band Downlink High Rate Data Only .......................................................................78

Table B-34: KD2 - K-band Downlink High Data w/ Ranging....................................................................79

Table B-35: PFC1a - Proximity Forward S-band Contingency .................................................................82

Table B-36: PFC1b - Proximity Forward S-band Contingency .................................................................82

Table B-37: PRC1a - Proximity Return S-band Contingency ....................................................................83

Table B-38: PRC1b - Proximity Return S-band Contingency ....................................................................83

Table B-39: CU1 - X-band Uplink Contingency.........................................................................................84

Table B-40: CU2 - X-band Uplink Contingency.........................................................................................84

Table B-41: CD1 - X-band Downlink Contingency ....................................................................................85

Table B-42: CD2 - X-band Downlink Contingency ....................................................................................85

Table C-1: LNSP SISE................................................................................................................................87

Table C-2: Proximity Link Supporting Signals...........................................................................................87

Table C-3: Proximity Link Supporting Signals...........................................................................................88

Table D-1: Message Identification .............................................................................................................89

Table D-2: LANS / AFS Messages..............................................................................................................93
LNIS V005 August 31, 2023 6

LIST OF TO BE DETERMINED AND TO BE REFINED

The table below lists specific To Be Determined (TBD) and To Be Refined (TBR) items in the LNIS 

document. These items are yet to be finalized or currently undefined at the release of this version. 

Each designator is numbered based on the document title, document version number when TBD/TBR was 

identified, parent section number, and number of the particular unresolved item. For example, “LNISTBD-6004” can be dissolved as – 4th unresolved TBD item identified in LunaNet Interoperability 

Specification Section 6. Once each item is dispositioned, the resolution will be substituted in place of the

designator and the item will be struckthrough (LNIS-TBD-6004) in this table. If new unresolved items are 

identified, it will be added to this table using the above defined designation scheme. All TBD/TBR will 

retain its original numbers and will not be renumbered as items are added or deleted. 

List of TBDs/TBRs

Designation Section Description

LNIS-TBD-3001 3.1.2 /Table 3: Bundle 

Protocol Service Interfaces

Applicable document needed for Bundles / 

TCPCL. Bundles are forwarded via TCP 

convergence layer adapter over TCP/IP.

LNIS-TBD-3002 3.1.2 /Table 3: Bundle 

Protocol Service Interfaces

Applicable document needed for Bundles / 

UDPCL - Bundles are forwarded via UDP 

convergence layer adapter over UDP/IP.

LNIS-TBD-3003 (incorporating 

LNIS-TBD-3004, LNIS-TBD3005, and LNIS4-TBD-3006)

3.3 Messaging Services Applicable document needed for 

Applicable document(s) needed for 

Messaging Services 

LNIS-TBD-3007 3.2.1.2 Pseudo-Range and 

Timing Reference 

Pseudo-noise (PN) codes as identified in 

CCSDS 414.1-B-2 and CCSDS 415.1-B-1 

have traditionally been employed for twoway ranging purposes. To use them as an 

option for one-way measurements, a 

method (TBD) must be set in place to 

convey information to the user correlating 

source PN phasing and the corresponding 

time of transmission.

LNIS-TBD-3008 3.2.1.3 Time-Transfer 

Reference

A standardized method (TBD) for a 

LunaNet node to provide a time reference 

will be implemented to allow users to have 

accurate time.

LNIS-TBD-3009 3.2.4.2 Range Measurement Frame ranging involves timestamping and 

identification of synchronized information 

frames. It is particularly useful in high-rate 

communications links, where elevated data 

frame rates facilitate more accurate time 

resolution. A frame ranging standard is 

TBD.
LNIS V005 August 31, 2023 7

Designation Section Description

LNIS-TBD-3010 3.2.5.2 Non-Regenerative 

Range Transponder

In addition to what is performed for the 

two-way Doppler transponder service, a 

non-regenerative transponder filters and remodulates the ranging signal onto the 

forward signal. The LNSP does not require 

knowledge of the ranging signal type 

employed by the user. The bandwidth 

allocated to the ranging signal and used by 

the LNSP for filtering shall be TBD.

LNIS-TBD-3011 3.2.6.1 Lunar Reference 

Frame

The use of a common lunar-centered, 

selenocentric reference frame across PNT 

services enables seamless consumption of 

the services, irrespective of specific LNSP 

or users. The lunar reference frame is 

described in detail in Lunar Reference 

Frame Standard (TBD).

LNIS-TBD-3012 3.2.6.2 Lunar Reference Time The use of a common lunar reference time 

across LNSP infrastructure elements is 

required to enable synchronization of 

services and time in the lunar domain. This 

common lunar reference time is described 

in detail in Lunar Time System Standard 

(TBD).

LNIS-TBD-3013-1 3.4.1 Lunar Search and 

Rescue (LunaSAR) Services

The distress message might include the 

position of the beacon (if determined 

through the PNT services) or the beacon 

position might be computed by the LNSP 

(or another actor) via triangulation of the 

beacon as received by multiple LNSP

nodes. A beacon might not know where the 

LNSP satellites are and might not have 

directive antenna capabilities, so the 

distress message might be broadcast and 

arrive at the LNSP with low power, this 

might require a dedicated, protected band, 

TBD.

LNIS-TBD-3013-2 3.4.2 Space Weather Alerting 

Services

Space Weather alerts and related messages 

will be communicated using the messaging 

services, per Appendix D. The specific 

standard alert and message content are still 

TBD.

LNIS-TBD-3014 3.6.2 User Initiated Services The User Initiated Services (UIS) process 

may be executed through service acquisition 

protocols utilizing a combination of 

previously scheduled services or available 

interfaces. These options are detailed in 

section 3.6.2 and are still being determined. 
LNIS V005 August 31, 2023 8

Designation Section Description

LNIS-TBD-3015 3.6.5 Link Establishment The standards for link establishment are

TBD and will likely vary depending on 

whether the user is accessing a Single 

Access or Multiple Access LunaNet 

service.

LNIS-TBD-4001 4. Lunanet Service Provider 

To User Interfaces

Standards for optical link interfaces are 

TBD.

LNIS-TBD-4002 4.1 LNSP-User Lunar Surface 

Interfaces

LS3 - Short-to-medium range wireless 

network with mobility and roaming 

utilizing 3GPP rel. 16 (and higher) (LTE 

and 5G TBD).

LNIS-TBD-4003 4.1 LNSP-User Lunar Surface 

Interfaces

Target Frequency Range is TBD for LS3, 

Short-to-medium range wireless network 

with mobility and roaming.

LNIS-TBD-4004 Appendix B/ Table B-19

PFS2 - Proximity Forward Sband Medium Rate w/ 

Ranging

Proximity Forward S-band Medium Rate 

w/ Ranging (PFS2) 2025-2110 MHz -

Fixed frequency assignments TBD.

LNIS-TBD-4005 4.2/ Table 8: LNSP-User 

Proximity Interfaces Spread 

Spectrum, Appendix B / 

Table B-19 PFS2 - Proximity 

Forward S-band Medium 

Rate w/ Ranging

Proximity Forward S-band Medium Rate 

w/ Ranging (PFS2) 2025-2110 MHz -

Symbol & Chip Rates TBD.

LNIS-TBD-4006 Appendix B / Table B-20: 

PRS2 - Proximity Return SBand Spread Spectrum

Proximity Return S-Band CDMA Return 

(PRS2) 2200-2290 MHz - Fixed frequency 

assignments TBD.

LNIS-TBD-4007 4.2/ Table 8: LNSP-User 

Proximity Interfaces Spread 

Spectrum, Appendix B / 

Table B-20: PRS2 -

Proximity Return S-Band 

Spread Spectrum

Proximity Return S-Band CDMA Return 

(PRS2) 2200-2290 MHz - Symbol & Chip 

Rates TBD.

LNIS-TBD-4008 4.2/ Table 8: LNSP-User 

Proximity Interfaces Spread 

Spectrum, Appendix B / 

Table B-22: PRS5 -

Proximity Return S-Band 

Multiple Access Return 

(MAR)

Proximity Return S-Band CDMA Return 

(PRS5) 2200-2290 MHz

Fixed frequency assignments TBD.

LNIS-TBD-4009 4.2/ Table 8: LNSP-User 

Proximity Interfaces Spread 

Spectrum, Appendix B / 

Table B-22: PRS5 -

Proximity Return S-Band 

Multiple Access Return 

(MAR)

Proximity Return S-Band CDMA Return 

(PRS5) 2200-2290 MHz

Symbol & Chip Rates TBD.
LNIS V005 August 31, 2023 9

Designation Section Description

LNIS-TBD-4010 4.2 / Table 7: LNSP-User 

Proximity Interfaces Single 

Access, Appendix B /Table 

B-11: PFK1 - Proximity 

Forward K-band Data Only

Proximity Forward Ka-band Data Only 

(PFKa1) 23.15-23.55 GHz

1 Msps ≤ Rs ≤ TBD

See Appendix B I.I Note [15]

LNIS-TBD-4011 4.2 / Table 7: LNSP-User 

Proximity Interfaces Single 

Access, Appendix B / Table 

B-12: PFK2 - Proximity 

Forward K-band Variable 

Coding and Modulation

Proximity Forward K-band Variable 

Coding and Modulation (PFK2) 23.15-

23.55 GHz

1 Msps ≤ Rs ≤ TBD Msps See Appendix B 

I.I Note [15]

LNIS-TBD-4012 4.2 / Table 7: LNSP-User 

Proximity Interfaces Single 

Access, Appendix B / Table 

B-13: PFK3 - Proximity 

Forward K-band High-Rate 

Data Only 

Proximity Forward K-band High-Rate Data 

Only (PFK3) 23.15-23.55 GHz

1 Msps ≤ Rs ≤ TBD Msps See Appendix B 

I.I Note [15]

LNIS-TBD-4013 4.2 / Table 7: LNSP-User 

Proximity Interfaces Single 

Access, Appendix B / Table 

B-14: PFK4 - Proximity 

Forward K-band High-Rate 

Data w/ Ranging 

Proximity Forward K-band High-Rate Data 

w/ Ranging (PFK4) 23.15-23.55 GHz

1.5 Msps ≤ Rs ≤ TBD Msps See Appendix 

B I.I Note [15]

LNIS-TBD-4014 4.2 / Table 7: LNSP-User 

Proximity Interfaces Single 

Access, Appendix B / Table 

B-15: PRK1 - Proximity 

Return K-band Data Only

Proximity Return K-band Data Only 

(PRK1) 27.0-27.5 GHz 1 Msps ≤ Rs ≤ 

TBD Msps See Appendix B I.I Note [15]

LNIS-TBD-4015 4.2 / Table 7: LNSP-User 

Proximity Interfaces Single 

Access, Appendix B / Table 

B-16: PRK2 - Proximity 

Return K-band Variable 

Coding and Modulation

Proximity Return K-band Variable Coding 

and Modulation (PRK2) 27.0-27.5 GHz 1 

Msps ≤ Rs ≤ TBD Msps 

See Appendix B I.I Note [15]

LNIS-TBD-4016 4.2 / Table 7: LNSP-User 

Proximity Interfaces Single 

Access, Appendix B / Table 

B-17: PRK3 - Proximity 

Return K-band High-Rate 

Data Only

Proximity Return K-band High-Rate Data 

Only (PRK3) 27.0-27.5 GHz 1 Msps ≤ Rs 

≤ TBD Msps See Appendix B I.I Note [15]

LNIS-TBD-4017 4.2 / Table 7: LNSP-User 

Proximity Interfaces Single 

Access, Appendix B / Table 

B-18: PRK4 - Proximity 

Return K-band High-Rate 

Data w/ Ranging

Proximity Return K-band Data w/ Ranging 

(PRK4) 27.0-27.5 GHz

1.5 Msps ≤ Rs ≤ TBD Msps See Appendix 

B I.I Note [15]
LNIS V005 August 31, 2023 10

Designation Section Description

LNIS4-TBD-4018 [LNIS V4] 4.2 / Table 9 -

Coding and Framing of 

Proximity Signals 

PFS/PRS 1e coding is TBD

Resolved, see Appendix B / Table B-5: 

PFS1e - Proximity Forward S-Band High 

Rate w/ Ranging, Table B-10: PRS1e - 

Proximity Return S-Band High Rate w/ 

Ranging

LNIS4-TBD-4019 [LNIS V4] 4.2 / Table 9 -

Coding and Framing of 

Proximity Signals 

PFS/PRS 1e frequency and rate is TBD

Resolved, see Appendix B / Table B-5: 

PFS1e - Proximity Forward S-Band High 

Rate w/ Ranging, Table B-10: PRS1e - 

Proximity Return S-Band High Rate w/ 

Ranging

LNIS-TBD-4020 Appendix B / Table B-22: 

PRS5 - Proximity Return SBand Multiple Access Return 

(MAR)

PRS5 Coding and Framing is TBD.

LNIS-TBD-4021 4.3/ Table 9: LNSP-User 

DWE signal interfaces, 

Appendix B / Table 

B-31: KU1 - K-band Uplink 

High Rate Data Only

K-band Uplink High Rate Data Only 

(KU1) Frequency Range 

& Symbol Rate - 22.55-23.15 GHz 2 Msps 

≤ Rs ≤ 50 Msps (Upper Limit TBD)

LNIS-TBD-4022 4.3/ Table 9: LNSP-User 

DWE signal interfaces, 

Appendix B / Table B-32: 

KU2 - K-band Uplink High 

Data w/ Ranging

K-band Uplink High Rate Data Only 

(KU2) Frequency Range 

& Symbol Rate 22.55-23.15 GHz 2 Msps ≤ 

Rs ≤ 50 Msps (Upper Limit TBD)

LNIS-TBD-4023 4.3/ Table 9: LNSP-User 

DWE signal interfaces, 

Appendix B / Table B-33: 

KD1- K-band Downlink High 

Rate Data Only

K-band Downlink High Rate Data Only 

(KD1) 25.5-27.0 GHz2 Msps ≤ Rs ≤ 200 

Msps [Upper Limit TBD], See Appendix 

B.ii Note [12] 

LNIS-TBD-4024 4.3/ Table 9: LNSP-User 

DWE signal interfaces, 

Appendix B / Table B-34: 

KD2 - K-band Downlink 

High Data w/ Ranging

K-band Downlink High Data w/ Ranging 

(KD2)25.5-27.0 GHz 2 Msps ≤ Rs ≤ 200 

Msps (Upper Limit TBD) See Appendix 

B.ii Note [12] 

LNIS-TBD-4025 Appendix B / Signal Interface 

Descriptions 

Applicable document for some signals are 

TBD. Standards development is an ongoing 

effort. See Appendix B.i.i Note [12], 

Appendix B.i.ii Note [6], Appendix B.ii 

Note [11], Appendix B.iii Note [7]

LNIS-TBD-6001 6.2 / Table 12 - LNSP–LNSP 

Crosslink Layer Interfaces

CFK1 Crosslink Forward Targeted 

Frequency Range is TBD 

23.15 – 23.55 GHz (TBD)
LNIS V005 August 31, 2023 11

Designation Section Description

LNIS-TBD-6002 6.2 / Table 12 - LNSP–LNSP 

Crosslink Layer Interfaces

CRK1 Crosslink Return Targeted 

Frequency Range is TBD 

27.00 – 27.50 GHz (TBD)

LNIS-TBD-6003 6.2 / Table 12 - LNSP–LNSP 

Crosslink Layer Interfaces

CFK1 Crosslink Forward Applicable 

Documents to be determined. 

LNIS-TBD-6004 6.2 / Table 12 - LNSP–LNSP 

Crosslink Layer Interfaces

CRK1 Crosslink Return Applicable 

Documents to be determinded. 

LNIS-TBD-AD0001 Applicable Documents [AD1] LunaNet and User Signal Structure 

Definition Document (TBD)

LNIS-TBD-AD0002 Applicable Documents [AD2] LunaNet Measurement Schema 

and Parameters Document (TBD)

LNIS-TBD-AD0003 Applicable Documents [AD3] LunaNet Detailed Message 

Definition Document (TBD)

LNIS-TBD-AD0004 Applicable Documents [AD4] LunaNet Location Services for 

Users Document (TBD)

LNIS-TBD-AD0005 Applicable Documents [AD5] Lunar Reference System and Lunar 

Time System Standard (TBD)

LNIS-TBD-AD0006 Applicable Documents [AD6] Reserved for Future Use

LNIS-TBD-AD0007 Applicable Documents [AD7] LunaNet LunaSAR Definition 

Document (TBD)

LNIS-TBD-AD0008 Applicable Documents [AD8] LunaNet Interoperability Security 

Specifications (TBD)

LNIS-TBR-3001 3.4.1 Lunar Search and 

Rescue (LunaSAR) Services

LunaSAR’s distress alert service is 

potentially received on PRS5 [TBR] and 

responded to over the PFS5 [TBR] links 

and are prioritized for rebroadcasting when 

received by the LNSP orbiting asset(s).

LNIS-TBR-4001 4.1 / Table 6 - LNSP–User 

Lunar Surface-Surface Link 

Layer Service Interfaces

For LS1 Short-range wireless network 

Targeted Frequency Range 5.150-5.835 

GHz (Lunar Near-side use only) (TBR)

under study.

LNIS-TBR-4002 [LNIS V4] 4.2 / Table 8–

LNSP–User Proximity Link 

Layer Service Interfaces] 

Proximity Forward S-Band Medium Rate 

w/ Ranging (PFS1b) Chip rate TBR. 

Resolved, see Appendix B Table B-2: 

PFS1b - Proximity Forward S-Band 

Medium Rate w/ Ranging
LNIS V005 August 31, 2023 12

Designation Section Description

LNIS-TBR-4004 [LNIS V4] 4.2 / Table 8–

LNSP–User Proximity Link 

Layer Service Interfaces

Proximity Forward S-Band Low-Rate w/ 

Ranging (PFS1c) 

See Appendix B. See CCSDS 401.0-B 

Section 2.2.4 for explanation of 

PCM/PSK/PM.

TBR: supplemental reference for 

implementation of PN ranging.

Presence of residual carrier aids 

demodulation (e.g., large doppler dynamics 

scenarios).

Resolved, see Appendix B Table B-3: 

PFS1c - Proximity Forward S-Band Low 

Rate w/ Ranging

LNIS-TBR-4005 4.2/ Table 8: LNSP-User 

Proximity Interfaces Spread 

Spectrum, Appendix B / 

Table B-19: PFS2 - Proximity 

Forward S-band Medium 

Rate w/ Ranging

Proximity Forward S-band Medium Rate 

w/ Ranging (PFS2) SS-BPSK CDMA 

(~3Mcps) or SS-UQPSK TBR.

LNIS-TBR-4006 [LNIS V4] 4.2 / Table 8–

LNSP–User Proximity Link 

Layer Service Interfaces

Proximity Return S-Band Medium Rate w/ 

Ranging (PRS1b) Chip rate TBR

Resolved, see Appendix B Table B-7: 

PRS1b - Proximity Return S-Band Medium 

Rate w/ Ranging

LNIS-TBR-4007 [LNIS V4] 4.2 / Table 8–

LNSP–User Proximity Link 

Layer Service Interfaces

Proximity Return S-Band Medium Rate w/ 

Ranging (PRS1b) 

See Note [1]

See CCSDS 401.0-B Section 2.2.7 for 

explanation of PCM/PM/bi-phase-L. TBR: 

supplemental reference for implementation 

of PN ranging. 

Resolved, see Appendix B Table B-7: 

PRS1b - Proximity Return S-Band Medium 

Rate w/ Ranging

LNIS-TBR-4008 4.2/ Table 8: LNSP-User 

Proximity Interfaces Spread 

Spectrum, Appendix B / 

Table B-20: PRS2 - 

Proximity Return S-Band 

Spread Spectrum4

Proximity Return S-Band CDMA Return 

(PRS2) SS-SQPN TBR.
LNIS V005 August 31, 2023 13

Designation Section Description

LNIS-TBR-4009 Appendix B / Table B-20: 

PRS2 - Proximity Return SBand Spread Spectrum4

Proximity Return S-Band CDMA Return 

(PRS2) Intent is for a wide beam spread 

spectrum return intended for P2P links. 

Similar to PRS5 but allows for higher data 

rates (less spreading) and ranging. There is 

a possibility to support multiple users 

simultaneously, albeit much less than 

PRS5. Signal parameters could also be 

modified for user specific needs (TBR).

See Appendix B.I.II Note [1].

LNIS-TBR-4010 4.2/ Table 8: LNSP-User 

Proximity Interfaces Spread 

Spectrum, Appendix B / 

Table B-22: PRS5 - 

Proximity Return S-Band 

Multiple Access Return 

(MAR)

Proximity Return S-Band CDMA Return 

(PRS5) SS-BPSK CDMA

(~3Mcps) or SS-UQPSK(Appendix C) 

TBR.

LNIS-TBR-4011 Appendix B / Table B-2: 

PFS1b - Proximity Forward 

S-Band Medium Rate w/ 

Ranging, Table B-7: PRS1b - 

Proximity Return S-Band 

Medium Rate w/ Ranging

PFS/PRS 1b uncoded is TBR

LNIS-TBR-4012 Appendix B / Table B-4: 

PFS1d - Proximity Forward 

S-Band High Rate Data Only, 

Table B-9: PRS1d - 

Proximity Return S-Band 

High Rate Data Only

PFS/PRS 1d uncoded is TBR

LNIS4-TBR-AP0001 Detailed Signal Definitions / 

Augmented Forward Signal 

Structure (PFS5)

To transmit a carrier center frequency of 

2492.028 MHz, the reference clock can be 

at 1.023MHz utilizing a reference clock 

multiplier of 2436. The detailed definition 

of the signal is provided in LunaNet and 

User Signal Structure Definition Document 

[AD1]. The AFS data rate is expected to be 

between 250sps and 1ksps (TBR).
LNIS V005 August 31, 2023 14

1 INTRODUCTION

LunaNet is envisioned as a network of cooperating networks (network of networks, akin to the terrestrial 

Internet) upon which providers can deliver communications, navigation, and other services for users on and 

around the Moon. LunaNet is based on a framework of mutually agreed-upon standards, protocols, and 

interface specifications that enable interoperability. LunaNet is intended to allow many lunar mission users 

to engage the services of diverse commercial and government service providers in an open and evolvable 

architecture. LunaNet Service Providers (LNSPs) can include communications, messaging, data 

transmission and distribution of position, navigation, timing, and situational awareness information.

LunaNet can be implemented by LNSPs as part of the earliest missions and accommodate expansion as 

new users and service providers come online. Many nations, agencies, and private companies can contribute 

to and participate in the establishment and operation of LunaNet-compatible services. Just as the terrestrial 

Internet has public and private networks, LunaNet will have public and private networks. Private networks 

may be separated out by a combination of physical connectivity and/or policy and security implementations.

This document, along with its companion documents, provides the basis for a comprehensive set of 

specifications used by LNSPs. LunaNet elements will include Earth ground stations, orbiting spacecraft, 

and lunar surface systems, and will allow LNSPs to service a variety of missions including those for human 

exploration, lunar science, commercial applications, and space technology. 

LunaNet will initially be instantiated by LNSPs comprised of a few nodes to meet the needs of early 

missions and evolve to meet the growing needs of a long-term lunar presence. All relay network services 

are not expected to be met by a single LunaNet-compatible spacecraft, or node. The expectation is that the 

needs of users will be met through a combination of interoperable commercial and government LNSPs. 

Interoperability across this network-of-networks can be achieved through negotiation of mutually-agreedupon standards that will be reflected in this document and in the specifications defined by other participants 

in the cooperative LunaNet. 

This current version of the document was written and reviewed by the National Aeronautics and Space 

Administration (NASA) and the European Space Agency (ESA).

1.1 PURPOSE 

The purpose of this specification is to define the standards and interfaces for LNSPs to administer

interoperable services to meet the needs of missions operating in the lunar vicinity. This document is not 

intended to replace either the International Communication System Interoperability Standards (ICSIS) or 

the Interagency Operations Advisory Group’s (IOAG) Lunar Communications Architecture Documents. 

This document specifies a set of standards for services so that users may design their systems with the 

expectation of interoperability with multiple providers and users. Any individual provider is not required 

to offer all services and interfaces in this document, but the aggregation of providers will have the interfaces 

and services described. It is also possible for providers to offer services and interfaces beyond what is 

described in this document. However, those services and interfaces will likely not be interoperable between 

service providers, thereby limiting the service options for a user on or around the Moon. 

This current document addresses all the LunaNet-compatible services, as currently identified. These 

services are expected to be met through a consortium of providers. To the extent that service providers 

follow the mutually-agreed-upon standards for the services and interfaces, which are reflected in this and 

applicable documents, the combined network can provide seamless services to multiple users.
LNIS V005 August 31, 2023 15

The services and interfaces addressed in this document will be deployed by LNSPs over time. Development 

and procurement activities that lead to implementation are expected to have their requirements 

specifications that reference the specific sections within this document. The use of this document as the 

basis for the requirements will enable interoperability, while the development and procurement activities 

define the phasing of the implementations. Initial developments and procurements will focus on the 

requirements needed to support the early human exploration missions and other lunar missions with low 

lunar orbiters and landers at the South Pole and far side as primary locations of interest. The evolution 

toward a long-term capability will be aligned with the plans for the increased human and robotic lunar 

missions.

LunaNet compliance is defined at the service or interface level. That is, a service or interface is “LunaNet 

compliant” if it conforms to the appropriate specification within this document and the applicable 

documents.

1.2 SCOPE 

This document defines the interoperable LunaNet standards and specifications for operations on the lunar 

surface and in cislunar space. International and commercial inputs are required to reach consensus on the 

contents of this document. 

This document will provide the necessary guidance for LNSPs and users to design and build interoperable 

systems. These standards and specifications are intended for broad use by all parties operating in cislunar 

space and will be levied as requirements on systems and services required to be interoperable.

1.3 SECURITY CONSIDERATIONS 

This section should be considered an informational reference as the LunaNet network continues to mature,

and the national and international community further defines interoperable security requirements. A 

LunaNet Interoperability Security Specifications [AD8], referenced at the end of this section, will be the 

repository for detailed implementation specifications. 

There are general expectations that users and providers shall protect the confidentiality, integrity, and 

availability of the systems, data, and communication pathways that will be part of LunaNet. These 

protections should be ensured using a combination of software and hardware that prevents unauthorized 

access, as well as corruption, interception, and loss of data. LNSP relays and nodes are also expected to 

have capabilities to enable rapid response to facilitate troubleshooting any communications anomalies.

 

United States National Institute of Standards and Technology (NIST) definitions for clarity:

• Confidentiality - Defined as preserving authorized restrictions on information access and 

disclosure, including ensuring the means for protecting personal privacy and proprietary 

information from access and disclosure.

• Integrity - Defined as guarding against improper information modification or destruction and 

includes ensuring information non-repudiation and authenticity.

• Availability - Defined as ensuring timely and reliable access to and use of information. 

Users are expected to protect their data through encryption and authentication mechanisms appropriate to 

the type of data they are transmitting and/or receiving. All user protocols with security enhancements will 

be required to comply with communications standards outlined in this document and shall not result in 

architectural changes to LunaNet.
LNIS V005 August 31, 2023 16

Network layer services, including but not limited to Internet Protocol (IP) and Bundle Protocol (BP), will 

be natively supported by LunaNet; this includes end-to-end data transport using IP security and BP security. 

All other data transport methods may be considered for approval with appropriate secure interfaces on a 

case-by-case basis for consideration and inclusion in the LunaNet Interoperability Specification.

Initially, the LunaNet infrastructure is likely to be implemented by LNSPs facilitating point-to-point (P2P) 

and broadcast links to specific sets of users. As a note, these users may make use of P2P and broadcast

services from one or multiple LNSPs simultaneously. LunaNet is planned to evolve to incorporate a 

network based on a delay/disruption tolerant networking (DTN) with several LNSPs operating with crosslinks between relays and creating multiple data flow paths. In the evolved DTN configuration, LNSPs will 

require jointly agreed DTN management and service orchestration policies to cover additional aspects such 

as bundle lifetimes, validity of routes, quality of service/prioritization, and network security management 

protocols. The administration and management of such a network in a secure manner will require 

Interconnection Security Agreements between LNSPs and associated space agencies/administering bodies 

in accordance with Consultative Committee on Space Data Standards (CCSDS) 350.4-G-2 Annex A.

LunaNet Interoperability Security Specifications [AD8] is under development. Once approved, this will be 

the authoritative source for interoperable LunaNet security requirements. 

1.4 APPLICABLE DOCUMENTS 

[AD1] LunaNet Signal-In-Space Recommended Standard - Augmented Forward Signal (LNIS-TBDAD0001)

[AD2] LunaNet Measurement Schema and Parameters Document (LNIS-TBD-AD0002)

[AD3] LunaNet Detailed Message Definition Document (LNIS-TBD-AD0003)

[AD4] LunaNet Location Services for Users Document (LNIS-TBD-AD0004)

[AD5] Lunar Reference System and Lunar Time System Standard (LNIS-TBD-AD0005)

[AD6] Reserved for Future Use

[AD7] LunaNet LunaSAR Definition Document (LNIS-TBD-AD0007)

[AD8] LunaNet Interoperability Security Specifications (LNIS-TBD-AD0008)

Other relevant documents:

CCSDS 702.1-B-1

CCSDS 734.1-B-1

CCSDS 133.1-B-3

CCSDS 414.1-B-2 

CCSDS 415.1-B-1

CCSDS 911.1-B-4

CCSDS 911.2-B-3

CCSDS 912.1-B-4

CCSDS 922.3-R-1

CCSDS 732.1-B-2 

CCSDS 231.0-B-4

CCSDS 401.0-B-31 

CCSDS 131.0-B-3

CCSDS 231.0-B-4
LNIS V005 August 31, 2023 17

2 LUNANET INTEROPERABILITY OVERVIEW

LNSPs provide interoperable communications and navigation - or position, navigation, and timing (PNT) -

services to user systems on and around the Moon. The Moon-based systems are referred to as the User 

Lunar Segment, and the users’ associated systems on Earth are referred to as the User Earth Segment. As 

seen in Figure 1, LunaNet has a Lunar Segment and an Earth Segment. The Lunar Segment contains 

elements that could either be in lunar orbit or on the lunar surface. Though they may be referred to in general 

as “lunar relays,” it is possible that some elements of the Lunar Segment may not provide any 

communications relay functions but support PNT or other non-data relay functions. 

The User Lunar Segment may interface with LunaNet by either a connection with an LNSP Lunar Segment 

or with the LNSP Earth Segment, or both. The LNSP Earth Segment is comprised of ground stations on 

Earth, possible Earth orbiting relays, and associated operations centers. Note that there are also interfaces 

between the LNSP Lunar Segment and the LNSP Earth Segment, these may be either intra-network, i.e., 

within a network provided by a single provider, or it may be inter-network, i.e., between cooperating 

providers. Standardization of the LNSP Lunar Relay-Earth Interface will enable the inter-network or cross 

support of lunar relay services by multiple providers. The LNSP Lunar Relay-Earth Interface, shown in 

Figure 1, is an intra-network example where a single provider in this case may use a non-standardized 

interface. The LNSP Lunar Relay-User Interface and LNSP -Direct-with-Earth Interface are standardized. 

The interface between the LunaNet Earth Segment and the User Earth Segment will also be standardized. 

Note that the user could provide a private direct link between its lunar and Earth segments. This is outside 

the scope of LunaNet interoperability and is not addressed in this specification.

Figure 1: LunaNet Segments
LNIS V005 August 31, 2023 18

Figure 2: LunaNet Standard Services and Interfaces between LNSPs and Users

Like the terrestrial internet, LunaNet will be built up through multiple LNSPs combined to provide services 

to users. To allow users to receive those services from any provider such that it appears as a single provider 

to that individual user, two categories of interoperable interfaces are required. See Figure 2. 

The first category is the LNSP-User Interface, which includes the service interfaces between a user and a 

provider. These include both the physical interfaces and the protocols and messages that provide services 

over those interfaces. A user shall be able to operationally receive the same service from different providers 

in the same way, such that the user will be able to use any connection as a LunaNet access point. Section 3

of this document describes the User Services and section 4 covers the LNSP to User Interfaces.

The second category is the LNSP – LNSP Interface. These include the physical interfaces and the protocols 

and messages that allow different LNSPs to work together to create the larger LunaNet infrastructure by 

augmenting individual LNSP capabilities with LNSP partners. Section 5 of this document describes the 

LNSP-to-LNSP Services and section 6 covers the LNSP-to-LNSP Interfaces.
LNIS V005 August 31, 2023 19

Figure 3: LunaNet Service Providers Interfaces

The LNSP interfaces are depicted in Figure 3. Each LNSP may have any combination of lunar surface, 

proximity, direct with Earth (DWE), and terrestrial interfaces with users. Interfaces between LNSPs may 

be any combination of lunar surface, crosslink, direct-with-Earth, and terrestrial interfaces. Lunar surface 

interfaces are interfaces between an LNSP lunar surface node and a user surface node. Proximity interfaces 

are between an LNSP lunar orbiting node and an orbiting or surface node. Note that the terms Direct-withEarth (DWE) and Direct-to-Earth (DTE) are considered synonymous in this document. DWE will be used 

in order to avoid ambiguity about directionality. This document identifies the standards to be used for the 

physical and service interfaces described above and depicted in red in Figure 3.

Table 1: Lunar Network Service Provider Interfaces

Interface Name Interface Description Document Section

LNSP-User Lunar Surface Interfaces Surface to surface interfaces between user 

and provider 4.1

LNSP-User Proximity RF Interfaces User interfaces with lunar orbiting provider 

nodes 4.2

LNSP-User DWE RF Interfaces Interfaces between user lunar systems and 

provider Earth systems 4.3

LNSP-User Contingency RF Interfaces Very low data rate proximity and DWE 

interfaces for contingency operations 4.4

LNSP-User Terrestrial Interfaces Terrestrial interfaces between user and 

provider 4.5

LNSP A-LNSP B Lunar Surface Interfaces Surface to surface interfaces between two 

LNSPs 6.1

LNSP A-LNSP B Crosslink Interfaces Interfaces between two LNSPs lunar 

orbiting nodes 6.2
LNIS V005 August 31, 2023 20

Interface Name Interface Description Document Section

LNSP A-LNSP B DWE Interfaces Interfaces between an LNSP lunar system 

and a different LNSP earth system 6.3

LNSP A-LNSP B Terrestrial Interfaces Terrestrial interfaces between two LNSPs 6.4
LNIS V005 August 31, 2023 21

3 USER SERVICES

3.1 COMMUNICATIONS SERVICES 

There are two communications service types. See Figure 4. Note that the service between and a source and 

destination may be provided by multiple nodes between the source and the destination. 

1. Real-time data services provide end-to-end data delivery between a source and destination with 

minimal delay. The latency on these services will be due to the signal travel time, any channel 

coding, and data operations only. 

2. Store-and-forward data services provide end-to-end data delivery with additional latency incurred 

by storage of data along the end-to-end path. This storage allows for the delivery of data when 

discontinuities or significant rate buffering occurs along the path. 

Figure 4: Two Types of Communications Services

Figure 5: User Application Simplified Protocol Stack

Figure 5 is a simplified view of the protocol stack options for LunaNet user applications. Note that this is a 

simplified view and intentionally does not include the full stack to streamline introductory discussions. The 
LNIS V005 August 31, 2023 22

applications are expected to be network-based using either the DTN BP or IP. However, a user application 

may use link layer services (dashed line) using the CCSDS Advanced Orbiting Systems (AOS) and USLP 

standards. The direct use of link layer services is intended for messaging services for LunaNet protocols

only and should be discouraged for user applications. Connections to a LunaNet access point over any 

available link will allow the user’s data to route to its destination. Though LunaNet permits link layer 

services, network-based applications will allow for the evolution and scalability of both user and provider 

systems.

3.1.1 REAL-TIME COMMUNICATIONS SERVICES 

Real-time communications services may be provided at both the link layer and the network layer. 

3.1.1.1 REAL-TIME LINK LAYER COMMUNICATIONS SERVICES

Link layer services will allow the relaying of data at the frame level and requires no processing of user data 

within those frames. This may be required due to user link layer security or to enable higher speed 

operations. The link layer service may include the multiplexing, de-multiplexing, and forwarding of user 

data frames. 

For interoperability, the link layer services will initially require CCSDS AOS frames. Future transition to 

variable length frame standard is planned to simplify multiplexing and de-multiplexing data frames for 

users having different frame lengths because AOS frames are fixed length. CCSDS Unified Space Data 

Link Protocol (USLP) has been included in this document with the intent to transition from AOS to USLP. 

AOS will continue to be supported. End-to-end delivery of data over a series of multiple links using link 

layer services will require pre-configuration of the full end-to-end path and is subject to interruption due to 

unplanned events.

3.1.1.2 REAL-TIME NETWORK LAYER COMMUNICATIONS SERVICES

Real-time network layer services provide end-to-end delivery of data over a series of multiple links with 

increased functionality and flexibility over the link layer services. The only network layer service 

guaranteed to provide end-to-end delivery to any network user is the DTN BP. However, operation 

assumptions for specific user applications will allow successful application support through real-time 

network layer services provided using the IP. Use of IP requires both the source and destination to be

operating within a portion of the network capable of supporting IP, such as the lunar surface. IP services 

are provided over AOS frames and USLP on the links described above or commercial standards, such as 

local wireless systems. Table 2 below provides a summary of the IP service interfaces. Since DTN BP also 

provides the store-and-forward communications services, the interfaces for BP services are described in

Table 3 in the following section.

Table 2: IP Service Interfaces

Interface Name Description Applicable Interfaces Applicable 

Documents

IP over CCSDS 

Encap/AOS

IP packets encapsulated 

using CCSDS encapsulation 

service and inserted into 

AOS frames

All AOS link layer service 

interfaces CCSDS 702.1-B-1
LNIS V005 August 31, 2023 23

Interface Name Description Applicable Interfaces Applicable 

Documents

IP over CCSDS 

Encap/USLP

IP packets encapsulated 

using CCSDS encapsulation 

service and inserted into 

AOS frames

All USLP link layer 

service interfaces CCSDS 702.1-B-1

IETF Standards IP packets over current 

terrestrial standards

All terrestrial standardbased interfaces

3.1.2 STORE-AND-FORWARD COMMUNICATIONS SERVICES 

Interoperable store-and-forward communications services will be provided by DTN BP. In situations where 

DTN nodes are connected via an IP network, lunar surface networks, terrestrial networks, and/or on-board 

networks, the DTN bundles can be carried via Transmission Control Protocol (TCP) or User Datagram 

Protocol (UDP) convergence layer protocols over standard terrestrial internet protocols (see section 

223.1.1.2). For those cases where no direct IP connection is available or not suitable due to the link 

characteristics, the DTN data bundles are carried by either a Licklider Transmission Protocol (LTP)

convergence layer with LTP segments encapsulated in encapsulation packets or directly in encapsulation 

packets, which will be carried over an AOS or USLP link layer (see section 3.1.1.1). Table 3 below provides 

a summary of these options.

Table 3: Bundle Protocol Service Interfaces

Interface Name Description Applicable Documents

Bundles / TCPCL Bundles are forwarded via TCP convergence layer 

adapter over TCP/IP LNIS-TBD-3001

Bundles / UDPCL Bundles are forwarded via UDP convergence layer 

adapter over UDP/IP LNIS-TBD-3002

Bundles / LTPCL Bundles are forwarded via LTP convergence layer 

adapter over Encapsulation Packet Protocol

CCSDS 734.1-B-1

CCSDS 133.1-B-3

Bundles / EPPCL Bundles are forwarded via EPP convergence layer 

adapter over Encapsulation Packet Protocol CCSDS 133.1-B-3

3.2 POSITION, NAVIGATION, AND TIMING SERVICES 

PNT services enable missions to determine position, velocity, or surface location, plan trajectories, execute 

maneuvers, and maintain accurate time with a timeliness sufficient to meet mission requirements. PNT 

services can be offered via a combination of standardized signals for Doppler, ranging, timing, and standard 

messages and protocols for the exchange of measurements and products. These are needed for safety, 

situational awareness, communication, and mission and science objectives. 

To offer these services and provide interoperability, the intent is to take maximum advantage of the 

communications links through judicious signal structure definitions. This can be accomplished in several 

ways. 
LNIS V005 August 31, 2023 24

One method is to provide PNT through dedicated communications links with a user. However, there is a 

need for lunar-global provisioning of PNT services to provide adequate geometry and appropriate time-tofirst fix to meet user requirements. 

Thus, a second method using an Augmented Forward Signal (AFS) provides PNT functionality independent 

of dedicated user communications links to enable multiple user reception of the signal simultaneously. 

Through the build-up of LunaNet nodes, this will establish a Lunar Augmented Navigation System (LANS)

as described in section 3.2.2, leading to a Global Navigation Satellite System (GNSS)-like capability for 

lunar PNT services. Similar to GNSS, a Code Division Multiple Access (CDMA) signal structure will be

used for the AFS communications link and can also be applied to dedicated proximity links. 

For communications links other than CDMA with a known transmit frequency, the receiver could measure 

the Doppler shift on the carrier. Non-CDMA links supported by pseudo-noise (PN) codes could provide an 

alternate method to derive pseudo-range measurements beyond the traditional two-way methods with 

ground source and measurement. In addition, a method whereby a specific data frame at an integer modulo 

1-second based on an accurate and stable time reference source can be used to provide pseudo-range and 

time-transfer capability on these links.

For full interoperability, additional specifications will be developed as follows:

1. LunaNet Signal-In-Space Recommended Standard - Augmented Forward Signal [AD1]

2. LunaNet Measurement Schema and Parameters Document [AD2]

3. LunaNet Detailed Message Definition Document [AD3]

4. LunaNet Location Services for Users Document [AD4]

5. Lunar Reference System and Lunar Time System Standard [AD5]

For effective interoperability in the PNT domain, the signal structures for LNSPs and users must be defined

[AD1], along with the implementation schemas for measurements [AD2] and lunar reference systems 

[AD5] for obtaining the measurements to ensure consistency in performance. 

Appendix D identifies the PNT services and associated messages required for interoperability. The specific 

service identifications are explained in the subsections of 3.2. The specifics of the messages will be defined 

in standard protocols used as part of the provision of the services [AD3]. Interoperability also relies on 

defining the formats and contents; transmission periodicity, cadence, and latency; and prioritization for the 

messages for each signal type and service. 

All PNT services described in sections 3.2.1 through 3.2.5 require the LNSP to have knowledge of the

position, velocity, and timing (PVT) of its own relay satellites, as well as future predicted values. This 

information is required to be forwarded to users for the consumption of the related services, in the form of 

messages MSG-G4 and MSG-G5. Appendix D identifies additional messages that can be used to inform a 

comprehensive state of LNSP node(s) or a user.

The PNT services can be grouped into two categories, as shown in Figure 6:

1. Dedicated Links: This group of services include all the options described in the following sections 

that are not broadcast in 2483.5-2500 Megahertz (MHz). These services are expected to be provided 

by direct links between the user and the provider. Not all links will provide all the services described 

in sections 3.2.1 and 3.2.3 - 3.2.5. A dedicated link can provide a reference signal for PNT 

observables with the associated messages. Alternatively, a signal that is not inherently designed to 

offer PNT observables may still be employed to transmit messages that support PNT.
LNIS V005 August 31, 2023 25

2. Lunar Augmented Navigation System (LANS): This service is provided from multiple provider 

nodes to multiple users at the same time, as described in section 3.2.2. The concept is similar to 

GNSS. This service is provided in 2483.5-2500MHz band via the AFS using the PFS5 signal. This 

service is expected to be provided with relatively large field-of-view antennas to cover a large part 

of the service volume with the same signal. The service will be composed of a collection of LNSP 

nodes aimed at achieving global lunar coverage of a minimum of four simultaneous LANS nodes 

in view at any given time. Users employing omnidirectional or hemispherical antennas can 

therefore receive signals from multiple LunaNet nodes simultaneously. It should be noted that 

LANS can also be implemented over a select (local) lunar region (e.g., South Pole), if the right 

number of vehicles (nodes) are in view at any given time.

Figure 6: PNT Services Provided by LNSP

The following sections define and describe the services available from reference signals, including the 

special case of LANS. Then the concept of measurement services is introduced, followed by transponder, 

supplemental, and finally, location services. The figures in these sections use an arrow to indicate the 

directionality associated with the notional image of a signal path.

3.2.1 REFERENCE SIGNALS 

LunaNet reference signals originate from an LNSP node, as depicted in Figure 7. These reference signals 

offer users the opportunity to derive measurements which describe the relative dynamics of the link between 

the LNSP reference source and the recipient. Defining the properties of each reference signal source enables 

users to derive pseudo-range, timing, and one-way Doppler observables through their receiver system.

Note: While a signal similar to a LunaNet reference signal may be initiated by a user, for clarity this useroriginating signal is not defined as a reference signal. Instead, the concept of a “one-way measurement 

service” is introduced in section 3.2.3. If a user transponds an LNSP reference signal, the LNSP node offers 

a “two-way measurement service” on that returned link as described in section 3.2.4.

A combination of one-way observables and related messages from different LunaNet-compatible sources

are utilized by a user’s in-situ navigation system to estimate the user’s PVT. A user may elect to 

complement LunaNet observations with other measurement types, but those are not addressed in this 

document.
LNIS V005 August 31, 2023 26

Figure 7: Reference PNT Signals Provided by an LNSP Node

3.2.1.1 ONE-WAY DOPPLER REFERENCE 

Most radio frequency communications links may be employed for the purposes of obtaining one-way 

Doppler measurements by a user, provided the user has accurate knowledge of the center frequency 

employed by the source. This is best accomplished with the use of a fixed frequency transmission. 

Differences in the measured frequency by the user will be due to Doppler, as well as frequency offsets from 

both LunaNet and user’s frequency oscillator sources. The LNSP source conveys reference frequency value 

and deviations via a message, as identified in Appendix D. 

3.2.1.2 PSEUDO-RANGE AND TIMING REFERENCE

The pseudo-range measurement approximates the distance between a LNSP source and the user’s receiver. 

The source emits a recognizable pattern at a given instant in time, which the user receives moments later, 

identifies, and timestamps. The delay measurement represents a one-way time of flight.

Depending on the characteristics of the communications link, these patterns will take the form of Pseudonoise (PN) sequences or high-rate frame synchronization and identification (i.e., frame ranging). Frame 

ranging is the term used in this document to refer to “telecommand/telemetry ranging,” with the telemetry 

ranging as defined in [RD24], and telecommand ranging definition proposed in [RD25]. While the latter is

currently a work in progress, PN sequences have been employed in satellite ranging technologies for quite 

some time. PN codes as identified in CCSDS 414.1-B-2 and CCSDS 415.1-B-1 have traditionally been 

employed for two-way ranging purposes. To use them as an option for one-way measurements, a method 

(LNIS-TBD-3007) must be set in place to convey information to the user correlating source PN phasing 

and the corresponding time of transmission. Signal structures like those utilized in Earth’s GNSS, such as 

PFS5 links described later in this document, include PN sequences that repeat an integer number of times 

each second. This establishes a simple method for the LNSP source to inform users of PN phasing and 

timing information to form a pseudo-range observation.

Pseudo-range measurements will include errors due to source and receiver time offsets, unaccounted 

equipment delays on both ends, and time dilation effects. Information concerning errors originating from 

the LNSP source is provided to users via messages as identified in the tables in Appendix D. 

3.2.1.3 TIME-TRANSFER REFERENCE 

A standardized method for a LNPS node to provide a time reference will be implemented to allow users to 

have accurate time. This is currently being developed in LNIS-TBD-3008. 

3.2.2 LUNAR AUGMENTED NAVIGATION SYSTEM (LANS) 

The AFS is a special case instantiation of the reference signals described in section 3.2.1. The compatible 

LNSP nodes will transmit the AFS, as described in section 3.6.4.1 and Appendix C, in the 2483.5-2500 
LNIS V005 August 31, 2023 27

MHz band (PFS5). A collection of LNSP nodes transmitting the AFS constitutes the LANS, which is 

illustrated in Figure 8.

LNSP nodes broadcasting AFS shall be synchronized among themselves and against a common reference 

time scale. Frequency offsets will be estimated against the reference by each provider. The user computes 

the time of arrival and frequency of the received CDMA signal by using the information provided in the 

broadcast navigation messages (e.g., ephemeris, clock corrections, and time and frequency information) to 

compute a pseudo-range, Doppler shift, and carrier phase. Considering the collection of observables from 

different LNSP nodes and the correlated broadcast navigation messages, the user can autonomously 

compute its position/velocity and the difference between the local receiver clock and the LNSP system 

reference clock. Appendix D contains the mapping of messages to the LANS via the AFS.

As with all other PNT services, a common lunar-centric reference frame and time system is defined per 

section 3.2.6. Each LNSP shall ensure they either implement these reference systems directly (e.g., signals 

are synchronized with the lunar reference time and the lunar reference frame with associated geodetic 

system components is used in the navigation products) or provide sufficient information to the user in the 

broadcast navigation messages to refer to these common reference systems (e.g., broadcast of the time 

offset of the specific LNSP time to the lunar reference time). 

Like GNSS, the LANS service will allow the user to compute code pseudo-ranges and carrier phase 

measurements from the AFS. Each LNSP shall ensure the AFS is provided with signal-in-space-error 

(SISE) within the maximum values specified in Appendix C, which allows users to derive reliable 

navigation solutions at a dependable level based on AFS signals from multiple LNSPs.

Figure 8: LANS PNT Concept Provided by LunaNet Nodes

The LANS via AFS is a multiple access forward link and allows reception by multiple users from the same 

LNSP node (one-to-many). Additionally, it also supports a many-to-one concept (i.e., GNSS-like with AFS 

signals from multiple LNSP nodes received by one user) owing to the mandatory time synchronization of 

the nodes, the coordinated generation of PNT-specific navigation messages, and the CDMA differentiation 

among the LNSP nodes. Further details about the AFS and the PFS5 signal structure are provided in 

Appendix C.
LNIS V005 August 31, 2023 28

The full LANS service volume, depicted in Figure 9, identifies the minimum global lunar space volume in 

which LANS services will be provided and performance must be met. However, an evolutionary approach 

is anticipated to build toward the full-service volume, with an expected start over the South Pole of the 

Moon. This is notionally shown in Figure 10 below. 

Figure 9: LANS Full-Service Coverage and Performance Volume

The LANS full-service volume includes lunar surface areas for all latitudes and altitudes out to a minimum 

of 200 kilometers above the surface for global coverage of the Moon. 

Figure 10: Notional LANS South Pole Service Coverage and Performance Volume
LNIS V005 August 31, 2023 29

3.2.3 ONE-WAY MEASUREMENTS 

One-way measurements performed by LNSP nodes are in reverse fashion to what is described in section 

3.2.1 and explained herein and depicted in Figure 11. The users generate signals similar to the construct 

of a LNSP-transmitted reference signal, so that they enable LNSP nodes to compute one-way Doppler and 

pseudo-range observables from the user. The resulting one-way measurement observables are forwarded to 

the necessary element via MSG-G13 messages, as identified in Appendix D. 

Note: A navigation system may elect to complement LNSP observations with other measurement types, but 

those are not addressed in this document. 

Figure 11: One-Way Measurements Performed by a LNSP Node

3.2.3.1 ONE-WAY DOPPLER MEASUREMENT

One-way Doppler measurements may be carried out for most incoming radio communications signals by 

tracking the frequency of the received signal and reporting the delta with respect to a defined source 

frequency. These measurements become valuable when the original frequency transmitted by the user is 

known. The quality of the measurement will depend on the stability of the user’s frequency source, as well 

as the signal-to-noise ratios of the received signal. Errors due to frequency offsets between user and LNSP

frequency references may be estimated by the corresponding navigation system. Users employ messages, 

as identified in Appendix D, to convey their transmitted frequency values and deviations. 

3.2.3.2 PSEUDO-RANGE MEASUREMENT

The pseudo-range measurement is as described in section 3.2.1.2, though for a measurement concept the 

user generates the constructed signal that is utilized by the measuring LNSP system to obtain a pseudorange observable. The LNSP system must be compatible with, and knowledgeable of, the ranging signal 

characteristics employed by the user as indicated in the LunaNet Signal-In-Space Recommended Standard 

- Augmented Forward Signal [AD1] interoperability specification.

Pseudo-range measurements will include errors due to source and receiver time reference offsets, and 

unaccounted phase delays and time corrections beyond what can be determined. The LNSP measurement 

system interprets information concerning these errors originating on the user end via user-provided 

messages, as indicated in Appendix D: MSG-G4. LNSP measurement systems are to be included in the 

corresponding observation messages, as indicated in Appendix D: MSG-G13. 
LNIS V005 August 31, 2023 30

3.2.4 TWO-WAY MEASUREMENTS 

Two-way measurements performed by LNSPs are similar to two-way radiometric services historically 

provided by the different tracking networks, such as the Near Space Network or Deep Space Network, 

where the tracking stations compare the transmitted and received signals to derive observations of roundtrip Doppler and range in terms of time-of-flight delay. In the current scenario, the LNSP node originates 

the transmit signal. These measurements require users to return a signal that is coherently related to the 

signal they received from the LNSP node, as illustrated in Figure 12 below. Range measurements can be 

supported by non-coherent, two-way communication interfaces by means of frame ranging as described in 

section 3.2.4.2 below.

Figure 12: Two-Way Measurements Performed by LNSP Node

Two-way measurement observations are disseminated to the required element via MSG-G13 messages, as 

indicated in Appendix D.

3.2.4.1 TWO-WAY DOPPLER MEASUREMENT

Two-way Doppler measurements require an LNSP to determine the differences in phase between 

transmitted and received signal center frequencies at predetermined time intervals. The user must 

coherently transpond the received frequency from LunaNet by implementing a predefined turn-around ratio. 

3.2.4.2 RANGE MEASUREMENT 

The range measurements performed by LNSPs can be separated into three categories: non-regenerative, 

regenerative, and frame ranging. Non-regenerative ranging, or transparent ranging, involves the user 

filtering and re-modulating the ranging signal onto the return signal. This method does not require the user 

to have prior knowledge of the ranging signal utilized for the service, only the frequency bandwidth 

allocated to it. The PN ranging signals described in CCSDS 414.1-B-2 may be used for this purpose.

Regenerative ranging involves PN code acquisition by the user and the return of a synchronized return PN 

ranging signal. It reduces the amount of noise present in the measurement, resulting in higher accuracies. 

The PN ranging signals described in CCSDS 415.1-B-1 and CCSDS 414.1-B-2 may be used for this 

purpose. Frame ranging involves timestamping and identification of synchronized information frames. It is 

particularly useful in high-rate communications links, where elevated data frame rates facilitate more 

accurate time resolution. A frame ranging standard is TBD (LNIS-TBD-3009).

3.2.5 TWO-WAY TRANSPONDER 

Two-way transponder services support a similar process as described in section 3.2.4, however, with the 

LunaNet and user roles reversed. In the transponder scenario, the user generates the source signal, and an 

LNSP node transponds that signal and returns it to the user, as depicted in Figure 13. Users must then be 

capable of performing the two-way Doppler and range measurements on the signal the LNSP sends back 

to them.
LNIS V005 August 31, 2023 31

Figure 13: Two-Way LNSP Node Transponder

3.2.5.1 TWO-WAY COHERENT DOPPLER TRANSPONDER 

In support of user two-way Doppler measurements, the LNSP node coherently relates its transmitted

frequency to the frequency received from the user. The turn-around ratios applied by LunaNet nodes are 

the inverse of the ratios employed by user transponders to maintain the frequency allocations assigned.

3.2.5.2 NON-REGENERATIVE RANGE TRANSPONDER

In addition to what is performed for the two-way Doppler transponder service, a non-regenerative LNSP

transponder filters and re-modulates the ranging signal onto the forward signal. The LNSP does not require 

knowledge of the ranging signal type employed by the user. The bandwidth allocated to the ranging signal 

and used by the LNSP for filtering shall be TBD (LNIS-TBD-3010).

3.2.5.3 REGENERATIVE RANGE TRANSPONDER 

The regenerative ranging transponder service involves PN code acquisition by the LNSP, followed by the 

transmission of a synchronized PN ranging signal transmitted to the user. The PN ranging signals described 

in CCSDS 415.1-B-1 and CCSDS 414.1-B-2 may be used for this purpose.

3.2.6 SUPPLEMENTAL NAVIGATION PRODUCTS 

Additional navigation products are defined to support the PNT services. Messages linked to such products 

are described in Appendix D. This section provides an overview of the supplemental navigation products.

3.2.6.1 LUNAR REFERENCE FRAME

The use of a common lunar-centered, selenocentric reference frame across LNSP PNT services enables 

seamless consumption of the services, regardless of specific LNSP or users. The lunar reference frame will 

be described in detail in Lunar Reference System Standard (LNIS-TBD-3011). Each LNSP shall either 

provide self PVT and ephemeris information in the common specified lunar reference frame or provide a 

means for the necessary coordinate transformations with respect to the specified lunar reference frame. 

3.2.6.2 LUNAR REFERENCE TIME

The use of a common lunar reference time across LunaNet elements is required to enable synchronization 

of services and time in the lunar domain. This common lunar reference time will be described in detail in 

Lunar Time System Standard (LNIS-TBD-3012). Each LNSP shall provide PNT services either directly 

synchronized with the Standard Lunar Time (SLT) or provide a means for the necessary time corrections 

to achieve Standard Lunar Time.
LNIS V005 August 31, 2023 32

3.2.6.3 LUNAR POTENTIAL MODEL

To ensure alignment for navigation services and products, a consistent set of coefficients that represent the 

lunar gravity model in degree and order will be defined in Lunar Reference System Standard (LNIS-TBDAD0005) and the coefficients can be distributed by LNSP provider nodes.

3.2.6.4 LUNAR ORIENTATION PARAMETERS

Similar to Earth Orientation Parameters, the oscillations of the lunar principal axis undergo precession and 

nutation that can be described in parametric form, this will be defined in Lunar Reference System Standard 

(LNIS-TBD-AD0005) and distributed by LNSP provider nodes.

3.2.6.5 CONSTELLATION ORBITAL PARAMETERS

To plan and acquire services from LNSP constellations, users need almanacs that provide coarse orbital 

information for each of the provider nodes. This covers the complete set including all LNSPs. In addition, 

there is a provision for LunaNet nodes to distribute ephemeris information for Earth-centric GNSS 

constellations in support of receivers using weak signals from the Earth-centric GNSS.

3.2.6.6 MAP DISSEMINATION

To serve the navigation needs of users, LunaNet can distribute messages that contain information on lunar 

maps. This covers sectored maplets, version numbers, and complete high-resolution digital elevation maps.

3.2.6.7 CONJUNCTION DATA

To aid space situational awareness and avoid collisions between resident space objects, LNSPs will 

disseminate conjunction data in MSG-G14.

3.2.6.8 ASSET SPECIFIC PARAMETERS

Information specific to either a provider node or a user may be needed to improve navigation knowledge 

and insight. This includes maneuver information, state estimation covariance, estimator state transition 

matrix, and attitude/orientation.

3.2.7 LOCATION SERVICE 

An LNSP can implement location services as part of their service portfolio. This service provides a 

computation of the user’s PVT based on observations received by the LNSP nodes and disseminates the 

product via MSG-G7. The LNSP capable of carrying out location services receives observations from 

multiple sources via MSG-G13. Other messages may be needed as a supplement if measurements were 

obtained by other LSNP assets, such as MSG-G4 and MSG-G1. These observations are routed to the 

navigation system responsible for deriving the user’s position and velocity, and potentially time. A request 

for location services includes necessary information for performing location or orbit determination for a 

specific user. Additional information on the location service will be defined in [AD4].
LNIS V005 August 31, 2023 33

3.3 MESSAGING SERVICES 

Messaging services will provide a standard way for messages to be transferred between a user node and 

provider node or between two provider nodes using any of the available interfaces. 

These messaging services will be utilized by LunaNet protocols. LunaNet protocols are protocols for 

service acquisition, PNT, network management, alerts, and other LunaNet services, such as space weather 

and LunaSAR. The messaging services are not intended for user data flows outside of LunaNet protocols. 

Though these data flows between a user and provider or between provider nodes may sometimes be 

referred to as “control plane data,” not all the protocols using the messaging resemble traditional control 

plane protocols. Note that the messages will be using the same physical links used for the user data. The 

number and type of LunaNet protocols is expected to evolve over time. The Messaging Service standard, 

LNIS-TBD-3003, will determine how LunaNet protocol messages are carried within any of the 

communications services and interfaces.

A generic use of the messaging service is shown below in Figure 14. Messages are being exchanged 

between a LNSP node and a user as part of the execution of a LunaNet protocol. The messages being 

exchanged are formatted within a standardized messaging format and carried over the standards to be 

defined.

Figure 14: LNSP Node and user exchange messages using messaging services

The messaging services will provide methods for identifying message priorities. A publish and subscribe 

capability may be used for this service, except for specific messages needed for PNT observables via the 

PNT reference signals described in section 3.2.1. The AFS link, described later in this document, will carry 

messages differently than the other space links due to the lower data rate available.

The specific standards for the messaging services are still being determined. Until the messaging services 

are in place, the LunaNet protocol messages will be transported along with the user application as depicted 

in Figure 5. For ease in interpreting the remainder of this document, the message IDs and titles are provided 
LNIS V005 August 31, 2023 34

in Table 4. Additionally, Appendix D provides information on the LunaNet protocol messages expected to 

be carried on the AFS link.

Table 4: Message ID and Titles

Message ID Message Title

MSG-G1 LunaNet Network Access Information

MSG-G2 Health and Safety

MSG-G3 MAntennaProperties

MSG-G4 SOrbit Ephemeris+Clock correction

MSG-G5 MOrbit Almanac

MSG-G6 SOrbit Almanac

MSG-G7 SOrbitState /Location

MSG-G8 Time of transmission

MSG-G9 Time and Frequency Synchronization (frame)

MSG-G10 Maneuver

MSG-G11 SAttitude State/Ephemeris

MSG-G12 MAttitudeEphem

MSG-G13 Observations

MSG-G14 Conjunction 

MSG-G15 Maplet

MSG-G16 Map Comprehensive

MSG-G17 Ancillary info

MSG-S18 Search and Rescue Alert

MSG-S19 Acknowledge- of SAR - LvL1

MSG-S20 Acknowledge- of SAR - LvL2

MSG-G21 User Message Request

MSG-G22 Acknowledge- of non-SAR MSG

MSG-G23 GNSS Augmentation 

MSG-G24 Detection Alert

MSG-G25 Science

MSG-G26 UIS Request

MSG-G27 UIS Response

MSG-G28 User Schedule Notice

MSG-G29 FF Commands

3.4 DETECTION AND INFORMATION SERVICES 

Detection and information services include LunaNet protocols within the network infrastructure to support 

alerts and critical information for user operations. Examples include space weather alerts triggered by 
LNIS V005 August 31, 2023 35

instrumentation within provider systems and Lunar Search and Rescue (LunaSAR) beacon detection and 

location. These applications would generate and transmit messages using the formats and interfaces 

described in Appendix D. These services would have standard messages specific to their functions, such 

that all users receiving the messages will be able to understand them. The messages would be communicated 

using the messaging services described in 3.3.

Table 5: Detection and Information Services

Service Description Required Interop Standards

LunaSAR Determines user location and gathers 

critical user status

LunaSAR Message Content / Format

Distress Message Prioritization

Possible signal design

Space Weather Alerts and other relevant information 

concerning Space Weather Space Weather Messages

3.4.1 LUNAR SEARCH AND RESCUE SERVICES 

LunaSAR services enable users to report location and distress information via internationally recognized 

messaging standards modelled after current state-of-the-art messaging content used in terrestrial search and 

rescue (SAR) activities. 

LunaSAR services require a combination of reception, prioritization, and re-broadcast/pass-through of 

distress messages on LNSP direct with Earth (DWE) and proximity links. LunaSAR message content is 

defined via inputs from the extravehicular activity (EVA) user community and SAR best practices. 

LunaSAR messages leverage rotating field definitions to reduce message size, allowing for robust lowdata-rate message transmissions from disadvantaged users to the LunaNet constellation at low power 

requirements and constrained link-budgets. LunaSAR services include location reporting of distress 

information, and low-data-rate bi-directional messaging between LunaSAR beacon users and message 

recipients such as Earth-based mission controllers, lunar surface assets, and lunar base camps.
LNIS V005 August 31, 2023 36

Figure 15: LunaSAR Data Path Concept of Operations

Four main steps describe the LunaSAR concept of operations and associated links:

1. Distress signal broadcast (beacon to LNSP link): The low power SAR beacon will transmit 

a distress signal that needs to be received by one or more LNSP nodes. The distress message 

might include the position of the beacon (if determined through the PNT services) or the beacon 

position might be computed by the LNSP (or another actor) via triangulation of the beacon as 

received by multiple LNSP nodes. A beacon might not know where the LNSP satellites are and 

might not have directive antenna capabilities, so the distress message might be broadcast and 

arrive at the LNSP with low power, this might require a dedicated, protected band. See Figure 

18.

2. Distress signal processing and start of rescue operation (LNSP node to Earth): The distress 

message is sent to Earth for processing and activation of the rescue operation. A return message 

to the distress source is generated. Note: in the future, a SAR control center might be located 

on the Moon’s surface.

3. LunaSAR return message (LNSP node to beacon link): The return message to the beacon 

is broadcast by the LNSP node. This message serves to inform the beacon that the distress 

message has been received and the rescue operation is ongoing. Considering the potential 

limitations of the user in terms of communications capabilities, the return message will be 

broadcast as part of the AFS signals but can also be provided via direct P2P links if available.

4. Rescue operation completion (links LNSP to/from beacon): During the rescue operation,

and until completion, there might be multiple activities and links being utilized (dedicated P2P 

communications links if available).

LunaSAR’s distress alert service is potentially received on PRS5 (LNIS4-TBR-3001) and responded to 

over the PFS5 (LNIS4-TBR-3001) links and are prioritized for rebroadcasting when received by the LNSP

orbiting asset(s). Prioritization aligns with the principles of terrestrial distress tracking services 

commercially available to those engaged in dangerous activities. 
LNIS V005 August 31, 2023 37

LunaSAR messages are notionally formatted in Concise Binary Object Representation (CBOR) formatting 

to allow for increased processing and transfer speeds between LunaSAR users and users. Note that rotating 

field messages described in this section are for example only and can be tailored to the specific lunar distress 

application/end-user hardware development. For example, message content would be derived from 

telemetry streams that could be monitored for faults and trigger automated distress message generation. 

(i.e., space suit pressure issue, radiation exposure, etc.) This process mimics current International Maritime 

Organization and International Civil Aviation Organization provisions for automated distress tracking and 

notification services and will be replicated as applicable within the lunar domain as the infrastructure 

evolves.

LunaSAR service broadcasts begin upon manual or automated triggering of distress transmissions and do 

not broadcast unless required. This aligns with the terrestrial standard for Cospas-Sarsat beacons and serves 

to preserve the nominal bandwidth within the relay system. Repetition rates following beacon/distress mode 

activation as well as signals and signal bandwidths used for the first step (distress beacon signal broadcast) 

are detailed in a separate document [AD7]. The PFS5 broadcast signals will include messages implementing 

the LunaSAR response to inform the distress beacon source that their request has been received and rescue 

actions are ongoing, this does not exclude sending the LunaSAR response also via other channels (e.g., P2P 

communication channels if available).

3.4.2 SPACE WEATHER ALERTING SERVICES 

Space weather alerts and related messages will be communicated using the messaging services, per 

Appendix D. The specific standard alert and message content are still TBD (LNIS-TBD-3013-2). Initiation 

of space weather alerts could be native to the LNSP node in lunar orbit if suitable instrumentation is present, 

or it could be received from another asset (space or Earth) and relayed accordingly to users in the lunar 

proximity.

3.5 SCIENCE SERVICES 

LNSP assets may be able to support science objectives by using available radio/optical links and telemetry. 

Some science services may only require that LNSP space equipment operate in a special mode within the 

capabilities of the communications and navigation subsystem. These services may require standardized 

message formats to collect and share measurements from the variety of possible LNSP systems.
LNIS V005 August 31, 2023 38

3.6 SERVICE ACCESS 

Figure 16: LunaNet Scheduling Interfaces Overview

Users will be able to access services through a variety of methods. See Figure 16. Services may be 

scheduled through an LNSP’s scheduling service that allows a mission operations center to pre-schedule 

services with a LNSP. Users that employ the services of more than one LNSP must schedule service 

separately with each LNSP and maintain their mission-specific combined schedule. Standardized methods 

for allowing one LNSP to schedule services with another LNSP on behalf of a user are desired. 

Users accessing Multiple Access links may still need some level of macro mission level scheduling. For 

example, the user needs to inform the LNSP so they can ensure assets are maintained and available. User 

Initiated Services (UIS) will allow users to request and receive services over links between the user and an

LNSP node. 

Space Frequency Coordination Group (SFCG) Provisional Recommendation: SFCG 42-1 defines the Sband frequency channel plan for lunar relay satellites such as LNSP nodes according to different service 

access methods1

. Future versions of the LNIS will clarify and specify the applicability of Recommendation 

SFCG 42-1 to the LNIS Service Access methods2

. The LunaNet Service Access methods are defined here 

in this context. The method of accessing the services can vary depending on the service access band.

1 Provisional Recommendation SFCG 42-1 defines frequency bands for S-band In-situ Lunar Relays only. It is 

anticipated that future revisions of the recommendation will define the frequency bands for K-band Lunar Relays, and 

it is planned that these recommendations will be adopted by LNIS when published.

2 There are some differences in use of terminology between the existing LNIS Service Access methods and the 

provisional SFCG 42-1. SFCG 42-1 is currently a provisional recommendation and the SFCG is collecting feedback 

from member space agencies, and LNIS planners will provide feedback to the SFCG on these items.
LNIS V005 August 31, 2023 39

3.6.1 EARTH-BASED SCHEDULING SERVICE 

Earth-based scheduled services are those where the request originates from the user’s Earth-based mission 

control center to the LNSP. The LNSP will make the necessary arrangements to confirm availability of the 

requested service given the available resources and then confirm the services scheduled with the user.

Each LNSP may have their own unique interface for Earth-based schedule requests. No standards for this 

interface have been identified yet. The CCSDS 902.1-B-1 Simple Schedule Format Specification is a 

starting point for the identification of the full standards required.

User services scheduled using the Earth-based scheduling service may access the service in the Single 

Access or Multiple Access bands allocated for lunar user proximity links defined by SFCG 42-1.

3.6.2 USER INITIATED SERVICES 

User Initiated Services (UIS) give lunar user assets the capability to autonomously access the lunar 

communications infrastructure to report periodic telemetries, inform on anomalies, and request services or 

network resources from the service provider. Additionally, it also allows mission owners/service providers 

to track user assets and task them at any time. 

Following the receipt of a UIS request, the LNSP will manage the request and allocate resources according 

to their availability, as well as established orchestration and service level agreement policies.

The UIS process may be executed through service acquisition protocols utilizing a combination of 

previously scheduled services or available interfaces. These options are detailed below and are still being 

determined (LNIS-TBD-3014):

• The Multiple Access Return link provides a highly available link for unscheduled access for 

initiating service requests.

• The AFS provides a highly available link for unscheduled network responses to requests.

• For UIS conducted using service acquisition protocols incorporating the Messaging Service, this is 

anticipated to be able to be conducted over any available communications path.

• An adaptation of the CCSDS Proximity-1 hailing process is under consideration as a physical 

mechanism for UIS. 

The use of a UIS protocol over messaging channels or through hailing methods would be used for any 

services in any frequency band. For example, K-band UIS might be possible using the S-band hailing 

method (i.e., dual band terminals) or a dedicated K-band hailing mechanism. Broadcast channels such as 

LANS could support UIS as well.

3.6.3 SINGLE ACCESS LINKS 

A variety of Single Access signal types are defined with specified signal parameters to provide a range of 

options supporting interoperability in terms of symbol rate, bandwidth efficiency, robustness, 

implementation complexity, and support for ranging. A summary of these signals is provided in Table 7 in 

section 4.2 with further signal specifications shown in Appendix B.

Single Access services in LunaNet are defined as those where an LNSP and a single user utilize a specific 

frequency channel to communicate on an exclusive basis, either for the duration of the session only or 

exclusively for the mission duration. This would be subject to agreement between the LNSP and user. In 

this context, Frequency Division Multiple Access and Time Division Multiple Access schemes are 
LNIS V005 August 31, 2023 40

collectively referred to as Single Access services. Single Access Links can be accessed through Earthscheduled or UIS means. 

3.6.4 SPREAD SPECTRUM LINKS 

There are two types of spread spectrum signal formats defined, one to provide low-rate CDMA services 

and another to provide medium rate P2P services with spread spectrum PN ranging. 

The broadcast forward signal PFS5 is referred to as the AFS. The PFS5 signal is unique in that it has a fixed 

frequency outside of the S-band proximity forward and return service bands and has a special role in 

navigation services. 

The CDMA return signal PRS5 is the signal interface of the Multiple Access Return (MAR) service. The

PRS5 signal operates with a fixed center frequency and high spreading ratio, allowing many users to share 

the channel. 

Other multiple access schemes that may be operated by LNSPs to deliver services, such as Frequency 

Division Multiple Access or Time Division Multiple Access are considered to be Single Access services in 

this context.

The spread spectrum signals PRS2 and PFS2 utilize a spread spectrum format similar to CDMA but are 

intended for P2P usage. They utilize a lower spreading ratio than PRS5 and PFS5, enabling higher data 

rates than the multiple access services.

Each of these signals will be further introduced in the following sections. Table 8 provides a summary of 

these signals, and further specifications are given in Appendix B. 

3.6.4.1 AUGMENTED FORWARD SIGNAL (AFS) SERVICE

A multiple access forward link is being implemented using the AFS design. The signal, represented as PFS5 

in the LNSP-User Proximity Interfaces and further described in Appendix C, will provide navigation and 

ancillary communications services simultaneously to multiple users in the lunar region without the need for 

a user to establish dedicated proximity links with a particular LNSP element. A single frequency will be 

used for the AFS signal and systems will be optimized to maximize coverage and availability for users. 

This optimization will likely lead to a lower available data rate, so the AFS data will be restricted to certain

LunaNet protocol messages, as defined in Appendix D. 

In addition, the AFS serves as an entry point to the LNSP network. Users entering the service volume 

acquire the AFS signal and obtain a coarse state of services available. This service enables LNSPsto provide 

users with important information and data, such as contact information, schedule, service availability, 

position of different LNSP elements, and acknowledgement of user requests or receipt of messages. Given 

the ubiquitous nature of the service, it serves as a dissemination channel for relevant notifications and alerts 

via provision of standard messages (3.3) and LunaSAR response messages (3.4.1).
LNIS V005 August 31, 2023 41

Figure 17: Augmented Forward Signal Service Provided by a Single LNSP Source

Refer to Appendix C for AFS signal structure definition and message requirements.

3.6.4.2 MULTIPLE ACCESS RETURN (MAR) SERVICE

The multiple access return link provides users with a highly available interface to initiate service requests, 

send situational awareness messages, or send SAR alerts through LNSP. Multiple access return links may 

also be used for low-rate user telemetry and science data. Refer to Appendix D for supporting message 

definitions. The PRS5 CDMA signal design will support simultaneous links from multiple users and the 

PNT functions described in section 3.2.

3.6.4.3 SPREAD SPECTRUM P2P SERVICES

Dedicated, medium data rate spread spectrum access links are specified in both forward and return 

directions (PFS2 and PRS2). These are intended for P2P links for real-time and store-and-forward data at 

a medium data rate and ranging. 

The intent is that the spreading ratios of these dedicated links can be customized to meet the user needs. As 

spread spectrum signals, there is a possibility that multiple users could share a single PFS2/PRS2 frequency 

channel with careful coordination. For example, a distributed science mission utilizing several instruments 

in near proximity may choose to utilize a single PRS2 channel that all science instruments share, enabling 

a simultaneous return on a single scheduled session. The symmetric nature of the signals permits two-way 

services. 

3.6.5 LINK ESTABLISHMENT 

Link establishment is required for both Earth-scheduled and UIS, although in the former case the process 

is simplified if the user and LNSP node are pre-configured with the necessary transceiver parameters. The 

standards for link establishment are TBD (LNIS-TBD-3015) and will likely vary depending on whether the 

user is accessing a Single Access or Multiple Access LunaNet service. 

The current UHF Proximity-1 protocol includes a hailing and link establishment mechanism which is under 

consideration for Single Access Services with regards to the S-band and Ka-band evolution of Proximity1. Note that Proximity-1 is under consideration as a standard for both UIS and Earth-scheduled Single 

Access services. This is to make use of the defined link establishment and hailing mechanism integral in 

the protocol, which includes the flexibility for demanded or negotiated link establishment and support for 

half-duplex and full duplex hailing. The use of an adapted CCSDS Proximity-1 Physical Layer Protocol3

3 Assuming a future evolution of CCSDS Proximity-1 Physical Layer Protocol 211.1-B to include extension of the 

Proximity-1 UHF Physical Layer protocol to additional frequency bands.
LNIS V005 August 31, 2023 42

for hailing on Single Access services will require a dedicated hailing channel to be reserved within the 

SFCG 42-1 bands.
LNIS V005 August 31, 2023 43

3.7 SERVICE COMBINED CAPABILITIES AND INTER-RELATIONSHIPS 

It is anticipated that users will be able to make productive service combinations to enhance and augment 

their communications and navigation capabilities. 

Examples of this approach include but are not limited to:

• Use of the LANS service by a lunar user to determine user position, relay position, and time 

synchronization in order to accurately point a directive antenna towards an LNSP relay and utilize 

the Communications Service.

• Use of the LANS service by a lunar user to maintain tracking for a directive antenna during a 

Communications Service session. 

• Delivery of Earth-scheduled session configuration information to a lunar user via the Messaging 

Service for configuration of a future real-time or store-and-forward communications session.

• Use of the One-Way Measurement or Two-Way Measurement service for Doppler and ranging 

measurements to establish a lunar user’s PVT or orbit determination in order to pre-configure the 

LNSP relay for a future Communications Services session.

• Use of the Communications Service to enhance or augment the AFS/LANS service, for instance to 

provide additional or higher accuracy navigation products, or distribution of authentication keys to 

the user.

The use of LNSP services in an inter-related manner is considered an opportunity to provide enhanced 

capabilities, however each service is considered independent in its own right from a service delivery 

perspective. LNSPs are encouraged to provide at least a basic means in their service delivery model for 

their services to be accessible to users without dependency on another service in order to maximize 

interoperability and provision for fallback and recovery scenarios.
LNIS V005 August 31, 2023 44

4 LUNANET SERVICE PROVIDER TO USER INTERFACES

The functional interfaces and corresponding frequency bands for lunar radio frequency links are shown in 

the following sections. Allowable signal bandwidths and power levels will be determined through the 

spectrum management process. Standards for optical link interfaces are TBD (LNIS-TBD-4001).

Communications link frequency ranges are specified in Figure 18.

Figure 18: LunaNet Interoperability Frequency Plan

The LunaNet spectrum architecture complies with the SFCG Recommendation 32-2R5 with the following 

notes:

• SFCG 32-2R5 allows use of both the near-Earth S-band (2025-2110 MHz forward, 2200-2290 

MHz return) and X-band (7190-7235 MHz forward, 8450-8500 MHz return) for DWE links 

between Earth and lunar regime. 

o However, due to increasing congestion in the S-band, LunaNet restricts use of S-band to 

lunar proximity links while X-band is used for DWE links. This enables reuse of the Sband in the cislunar region.

• SFCG 32-2R5 identifies several frequency band allocations that have not been approved by the 

International Telecommunication Union Radiocommunication Sector (ITU-R) in its regulations, 

including:

o Lunar Surface Wireless Network: Frequency bands for proposed cellular service based on 

3rd Generation Partnership Project (3GPP – The Mobile Broadband Standard) standards 

are under investigation.

o Lunar Orbit Radio Navigation Satellite Service (RNSS) to Lunar Surface: Use of the 5010-

5030 MHz band for PNT service requires ITU-R action.

• SFCG 32-2R5 includes use of optical communications links. LNIS anticipates including optical 

links in the future but does not address them in this version.
LNIS V005 August 31, 2023 45

4.1 LNSP-USER LUNAR SURFACE INTERFACES 

This section provides a list of the lunar surface signal interfaces. 

Table 6: LNSP–User Lunar Surface-Surface Link Layer Service Interfaces

Interface 

name Interface Type Description Targeted Frequency Range1 Applicable Documents

LS1 Short-range wireless 

network

Wi-Fi 6, 

Wi-Fi Certified AC

5.150-5.835 GHz 

Lunar near-side only

LNIS4-TBR-4001

CCSDS 883.0-B-1

SFCG 32-2R5

LS2 Short-range wireless 

network

Wi-Fi 6, 

Wi-Fi Certified N 2.4-2.48 GHz CCSDS 883.0-B-1

SFCG 32-2R5

LS3

Short-to-medium 

range wireless 

network with 

mobility and 

roaming

3GPP rel. 16 (and higher)

LTE and 5G 

LNIS-TBD-4002

LNIS-TBD-4003 CCSDS 883.0-B-1

[1] The exact frequency channel(s) have not been determined and are subject to coordination.

[2] SFCG 32-2R5 identifies the need to provide sufficient out of band filtering to protect the 2483.5-2500

MHz lunar orbit to lunar surface PNT band. 

A. Potential 3GPP bands should not overlap with SRS, SOS, ISS, RAS, RNSS, and RDSS bands, as 

defined by the SFCG.

B. In wireless communications using 3GPP, uplink / reverse link is defined as a lunar surface user 

(astronaut/rover) to a lunar surface base station (lander/tower). The downlink / forward link is defined 

as a lunar surface base station (lander/tower) to a lunar surface user (astronaut/rover).

C. 5.25-5.57GHz is allocated to SRS (active) on a primary basis; use of these frequencies for 

communications in the lunar region is on a non-interference and unprotected basis to SRS (active).

 
LNIS V005 August 31, 2023 46

4.2 LNSP-USER PROXIMITY INTERFACES 

This section provides an overview of the signal formats across proximity links between LNSPs and users. 

A summary of the single access proximity signal interfaces is shown in Table 7. The full specification of 

each signal is found in Appendix B. The ID column is used to identify the unique signal interfaces described 

in Appendix B. The ID values in the tables are hyperlinked to provide quick navigation to the relevant 

section of Appendix B. 

Table 7: LNSP-User Proximity Interfaces Single Access

Frequency ID Modulation Symbol Rate Ranging Summary

S-band

Forward

2025-2110 

MHz

PFS1a Filtered BPSK Min: 2 ksps 

Max: 2.048 Msps No BPSK modulation common on existing S-band links.

PFS1b PCM/PM Min: 48 ksps 

Max: 1.024 Msps

PN 

Ranging

Data on carrier, option for ranging on 

residual carrier. Medium Data Rates.

PFS1c PCM/PSK/PM Min: 0.5 ksps 

Max: 48 ksps

PN 

Ranging

Data on subcarrier, option for ranging 

on residual carrier. Low Data Rates.

PFS1d Filtered OQPSK 

or GMSK

Min: 1 Msps 

Max: 5 Msps No Higher order modulation for higher data rates, without ranging.

PFS1e GMSK+PN Min: 1 Msps 

Max: 5 Msps 

PN 

Ranging

GMSK+PN per CCSDS standards. 

High Data Rates w/ Ranging.

Return

2200-2290 

MHz

PRS1a Filtered BPSK Min: 2 ksps 

Max: 2.048 Msps No BPSK modulation common on existing S-band links.

PRS1b PCM/PM Min: 48 ksps 

Max: 1.024 Msps

PN 

Ranging

Data on carrier, option for ranging on 

residual carrier. Medium Data Rates.

PRS1c PCM/PSK/PM Min: 0.5 ksps 

Max: 48 ksps

PN 

Ranging

Data on subcarrier, option for ranging 

on residual carrier. Low Data Rates.

PRS1d Filtered OQPSK 

or GMSK

Min: 1 Msps 

Max: 5 Msps No Higher order modulation for higher data rates, without ranging.

PRS1e GMSK+PN Min: 1 Msps 

Max: 5 Msps 

PN 

Ranging

GMSK+PN per CCSDS standards. 

High Data Rates w/ Ranging.

K-band

Forward

23.15-23.55 

GHz

PFK1 Filtered BPSK Min: 1 Msps 

Max: 2.048 Msps No BPSK given as option for simplest, low-rate Ka-band system.

PFK2 DVB-S2, SCCC, 

or LDPC-VCM

Min: 1 Msps

Max: {TBD} No VCM schemes enable spectrally efficient higher data rates.

PFK3 Filtered OQPSK 

or GMSK

Min: 1 Msps

Max: {TBD} No OQPSK (or GMSK) modulation common on existing K-band links.

PFK4 GMSK+PN Min: 1.5 Msps

Max: {TBD} 

PN 

Ranging

GMSK+PN per CCSDS standards. 

High Data Rates w/ Ranging.

Return

27.0-27.5 

GHz

PRK1 Filtered BPSK Min: 1 Msps 

Max: 2.048 Msps No BPSK given as option for simplest, low-rate Ka-band system.

PRK2 DVB-S2, SCCC, 

or LDPC-VCM

Min: 1 Msps

Max: {TBD} No VCM schemes enable spectrally efficient higher data rates.

PRK3 Filtered OQPSK 

or GMSK

Min: 1 Msps

Max: {TBD} No OQPSK (or GMSK) modulation common on existing K-band links.

PRK4 GMSK+PN Min: 1.5 Msps

Max: {TBD} 

PN 

Ranging

GMSK+PN per CCSDS standards. 

High Data Rates w/ Ranging.
LNIS V005 August 31, 2023 47

A summary of the spread spectrum proximity signal interfaces is shown in Table 8. The full specification 

of each signal is found in Appendix B. The ID column is used to identify the unique signal interfaces 

described in Appendix B. The ID values in the tables are hyperlinked to provide quick navigation to the 

relevant section of Appendix B. 

Table 8: LNSP-User Proximity Interfaces Spread Spectrum

Frequency ID Modulation Symbol Rate Ranging Summary

S-band

Forward

2025-2110 GHz

PFS2

SS-BPSK 

{TBD}

{TBD} Spread 

spectrum PN

Spread spectrum PN w/ ranging, 

low spreading ratio for medium data 

rates.

Return

2200-2290 MHz

PRS2

SS-BPSK 

{TBD}

{TBD} Spread 

spectrum PN

Spread spectrum PN w/ ranging, 

low spreading ratio for medium data 

rates.

Return

2200-2290 MHz

Fc: {TBD}

PRS5

SS-BPSK 

{TBD}

{TBD} Spread 

spectrum PN

Multiple Access Return (MAR). 

Spread spectrum PN w/ ranging, 

high spreading ratio for low data 

rates, many users.

AFS

Fc: 2492.028 MHz

BW: 16.5 MHz PFS5 SeeAppendix C

See

Appendix C

See

Appendix C

See Lunar Augmented Navigation 

System (LANS)
LNIS V005 August 31, 2023 48

4.3 LNSP-USER DWE INTERFACES 

A summary of the DWE signal interfaces is shown in Table 9. DWE applies both to direct links between 

Earth and lunar surface and links between Earth and LunaNet relay nodes. 

In this document the special case of the link between a lunar relay orbiter and Earth station is identified as 

the “trunk link.” A trunk link exists in both the forward and return directions. The full specification of each 

signal is found in Appendix B. The ID field is used to identify the unique signal interfaces described in 

Appendix B. The ID values in the tables are hyperlinked to provide quick navigation to the relevant section 

of Appendix B. 

Table 9: LNSP-User DWE signal interfaces

Frequency ID Modulation Symbol Rate Ranging Summary

X-band

Uplink 

7190-7235 

MHz

XU1 PCM/PM Min: 64 ksps 

Max: 1.024 Msps

PN 

Ranging

Data on carrier, option for ranging on 

exposed residual carrier. Medium Data 

Rates.

XU2 GMSK+PN Min: 150 ksps 

Max: 1 Msps

PN 

Ranging

GMSK+PN per CCSDS standards. 

High Data Rates w/ Ranging.

XU3 PCM/PSK/PM Min: 0.5 ksps 

Max: 64 ksps

PN 

Ranging

Data on subcarrier, option for ranging 

on residual carrier. Low Data Rates.

XU4 Filtered OQPSK 

or GMSK

Min: 128 ksps 

Max: 10 Msps No Higher order modulation for higher 

data rates, without ranging.

Downlink 

8450-8500 

MHz

XD1 PCM/PM Min: 64 ksps 

Max: 1.024 Msps

PN 

Ranging

Data on carrier, option for ranging on 

exposed residual carrier. Medium Data 

Rates.

XD2 GMSK+PN Min: 150 ksps 

Max: 1 Msps

PN 

Ranging

GMSK+PN per CCSDS standards. 

High Data Rates w/ Ranging.

XD3 PCM/PSK/PM Min: 0.5 ksps 

Max: 64 ksps

PN 

Ranging

Data on subcarrier, option for ranging 

on residual carrier. Low Data Rates.

XD4 Filtered OQPSK 

or GMSK

Min: 128 ksps 

Max: 10 Msps No Higher order modulation for higher 

data rates, without ranging.

K-band

Uplink 

22.55-23.15 

GHz

KU1 Filtered OQPSK 

or GMSK

Min: 2 Msps 

Max: 50 Msps 

{TBR}

Frame 

Ranging

OQPSK (or GMSK) modulation 

common on existing K-band links.

KU2 GMSK+PN

Min: 2 Msps 

Max: 50 Msps 

{TBR}

PN 

Ranging

GMSK+PN per CCSDS standards. 

High Data Rates w/ Ranging.

Downlink

25.5-27.0 

GHz

KD1 Filtered OQPSK 

or GMSK

Min: 2 Msps 

Max: 200 Msps 

{TBR}

Frame 

Ranging

OQPSK (or GMSK) modulation 

common on existing K-band links.

KD2 GMSK+PN

Min: 2 Msps 

Max: 200 Msps 

{TBR}

PN 

Ranging

GMSK+PN per CCSDS standards. 

High Data Rates w/ Ranging.
LNIS V005 August 31, 2023 49

4.4 LNSP-USER CONTINGENCY INTERFACES 

A summary of the contingency mode signal interfaces is shown in Table 10. Contingency mode 

signals are those used during off nominal or emergency states when power is limited, or antenna 

pointing is compromised. The full specification of each signal is found in Appendix B. The ID column

is used to identify the unique signal interfaces described in Appendix B. The ID values in the tables are 

hyperlinked to provide quick navigation to the relevant section of Appendix B. 

Table 10: LNSP-User Contingency Mode Signal Interfaces

Frequency ID Modulation Symbol Rate Ranging Summary

Proximity S-band

Forward

2025-2110 

MHz

PFC1a PCM/PSK/PM 15.625 sps PN 

Ranging

Data on subcarrier, option for ranging on 

residual carrier. Lowest rate used for very 

weak signal links.

PFC1b PCM/PSK/PM 250 sps PN 

Ranging

Data on subcarrier, option for ranging on 

residual carrier. Higher rate to provide 

flexibility in cislunar space. 

Return

2200-2290 

MHz

PRC1a PCM/PSK/PM 15.625 sps PN 

Ranging

Data on subcarrier, option for ranging on 

residual carrier. Lowest rate used for very 

weak signal links.

PRC1b PCM/PSK/PM 250 sps PN 

Ranging

Data on subcarrier, option for ranging on 

residual carrier. Higher rate to provide 

flexibility in cislunar space. 

DWE X-band

Uplink 

7190-7235 

MHz

CU1 PCM/PSK/PM 15.625 sps PN 

Ranging

Data on subcarrier, option for ranging on 

residual carrier. Lowest rate typically used 

for deep space.

CU2 PCM/PSK/PM 250 sps PN 

Ranging

Data on subcarrier, option for ranging on 

residual carrier. Higher rate to provide 

flexibility in cislunar space. 

Downlink 

8450-8500 

MHz

CD1 PCM/PSK/PM 20 sps PN 

Ranging

Data on subcarrier, option for ranging on 

residual carrier. Lowest rate typically used 

for deep space.

CD2 PCM/PSK/PM 250 sps PN 

Ranging

Data on subcarrier, option for ranging on 

residual carrier. Higher rate to provide 

flexibility in cislunar space. 
LNIS V005 August 31, 2023 50

4.5 LNSP-USER TERRESTRIAL INTERFACES 

A summary of the signal interfaces between the LNSP and the user mission operation centers on Earth 

are shown in Table 11 below.

Table 11: LNSP–User Terrestrial Link Layer Service Interfaces

Service Interface 

ID Interface Type Applicable Documents

SLE RAF Space Link Extension Return All Frames CCSDS 911.1-B-4

SLE RCF Space Link Extension Return Channel Frames CCSDS 911.2-B-3

SLE FCLTU Space Link Extension Forward CLTU CCSDS 912.1-B-4

CSTS FFS Cross Support Transfer Service Forward 

Frame Service CCSDS 922.3-R-1
LNIS V005 August 31, 2023 51

5 LUNANET SERVICE PROVIDER TO LUNANET SERVICE 

PROVIDER SERVICES

5.1 LNSP A-LNSP B COMMUNICATIONS SERVICES 

Using standard interfaces, an LNSP will be able to provide the communications services described in 

section 3.1. This will enable LunaNet-compatible communications service infrastructure to be provided 

by multiple providers. Beyond the user data, there will be communications between LNSPs for 

scheduling, routing, asset availability, and other functions.

5.2 LNSP A-LNSP B PNT SERVICES 

PNT services, as described in section 3.2 Position, Navigation, and Timing Services, may also be 

provided between assets belonging to two different LNSPs. This will be addressed in next version. 
LNIS V005 August 31, 2023 52

6 LUNANET SERVICE PROVIDER TO LUNANET SERVICE 

PROVIDER INTERFACES

6.1 LNSP A-LNSP B LUNAR SURFACE INTERFACES 

These interfaces will follow the same standards as identified in section 4.1 LNSP-User Lunar Surface 

Interfaces. 

6.2 LNSP A-LNSP B CROSSLINK INTERFACES 

To allow end-to-end delivery of data of user data, cross-link interfaces shall be based on DTN BP for 

the network layer. Crosslinks will allow two LNSPs to pass user data between their assets, message 

between the assets, and provide PNT services. 

LunaNet providers will be required to directly exchange information within the internal architecture, 

independently from DWE interfaces, to enable awareness of the overall service health, availability and 

status, current and future schedule, and time synchronization. Direct exchange of information within 

the LunaNet architecture will also allow for the use of observables for self-navigation purposes. This 

section will cover the required interfaces between providers to ensure resilient services independent 

from Earth links. These crosslinks are to be carefully designed such that they are compatible with user 

links (TBD).

Table 12: LNSP–LNSP Crosslink Layer Interfaces4

Interface 

Name

Interface 

Type

Targeted 

Frequency Range3 Modulation4 Coding4 Applicable Documents2

CFK1 Crosslink 

Forward1

23.15 – 23.55 GHz 

(LNIS-TBD-6001)

Filtered 

OQPSK and 

GMSK2

LDPC rate 1/2 (4096 octets 

plus 64-bit ASM)

LDPC code rate 4/5 (2560 

octets plus 64-bit ASM)

LDPC rate 7/8 (1020 octets 

plus 32-bit ASM)

LNIS-TBD6003

CRK1 Crosslink 

Return1

27.00 – 27.50 GHz 

(LNIS-TBD-6002)

Filtered 

OQPSK and 

GMSK2

LDPC rate 1/2 (4096 octets 

plus 64-bit ASM) 

LDPC code rate 4/5 (2560 

octets plus 64-bit ASM)

LDPC rate 7/8 (1020 octets 

plus 32-bit ASM)

LNIS-TBD6004

[1] The “forward” or “return” designation is determined by the source and destination of a particular

signal. If a signal originates at a lunar region user (orbiter, rover, lander, etc.) and is sent to LNSP-A, 

any subsequent links to LNSP-B, LNSP-C, etc. before being routed to a mission or science operations 

center would be at a “return” frequency (27.0 – 27.5 GHz). If data was sent by a science or mission 

operations center via an LNSP Earth station, then passed around nodes within an LNSP network before 

being delivered to a lunar region user, the links between LNSP nodes in this case would be at a 

“forward” frequency (23.15 – 23.55 GHz). Each LNSP will have the capability to transmit as well as 

receive crosslink signals from fellow LNSPs that are part of the service provider network.
LNIS V005 August 31, 2023 53

[2] See CCSDS Preliminary Recommendation 2.2.10 on “High-Rate Space-to-Space Links, Space 

Research and Inter-Satellite.”

[3] Exact center frequency to be determined based on user requirements and concept of operations and 

are subject to coordination.

[4] Preliminary recommendations are TBD.

6.3 LNSP A-LNSP B DWE INTERFACES 

These interfaces will follow the same standards as identified in 4.3 LNSP-User DWE Interfaces.

6.4 LNSP A-LNSP B TERRESTRIAL INTERFACES 

These interfaces will follow the same standards as identified in section 4.5 LNSP-User Terrestrial 

Interfaces.
LNIS V005 August 31, 2023 54

7 REFERENCES AND APPENDICES 

[RD1]Anzalone, E., et al. “Lunar Navigation Beacon Network using GNSS Receivers”, Proceedings 

of the 70th International Astronautical Congress (IAC), Washington, DC, October 2019.

[RD2] Ashman, B., et al. “Exploring the Moon with GNSS: Applications of GNSS within and Beyond 

the Space Service Volume.”

[RD3] CCSDS, 730.1-G-1, Solar System Internetwork (SSI) Architecture, Informational Report, 

Green Book, Issue 1, July 2014. 

[RD4] Cheung, K., Lee, C., “Lunar Relay Coverage Analysis for RF and Optical Links,” AIAA 

SpaceOps 2018 Conference, 31 May 2018.

[RD5] D. J. Israel et al., "LunaNet Architecture and Concept of Operations," The 16th International 

Conference on Space Operations (SpaceOps 2021), 2021.

[RD6] Dille, M., et al. “PHALAX: Expendable Projectile Sensor Networks for Planetary Exploration”, 

2020 IEEE Aerospace Conference, Big Sky, MT, 2020. 

[RD7] Ely, T., et al. “The Deep Space Atomic Clock Mission”, 23rd International Symposium on 

Space Flight Dynamics, Pasadena, California, October 29 - November 2, 2012, 

http://hdl.handle.net/2014/43016. 

[RD8] Heckler, G., Gramling, C., Donaldson, J., Baldwin, P., “TDRSS Augmentation Service for 

Satellites,” Proceedings of the 14th International Conference on Space Operations, 16-20 May 2016, 

Daejeon, Korea

[RD9] International Communication System Interoperability Standards (ICSIS) Rev A, September 

2020.

[RD10] IOAG “Space Internetworking Strategy Group (SISG) Recommendations on the Selection of 

End-to-end Space Internetworking Protocol,” IOAG Report, February 2021.

[RD11] IOAG “The Future Lunar Communications Architecture v1.3,” Report of the IOAG Lunar 

Communications Architecture Working Group, January 2022.

[RD12] Israel, D. et al., “LunaNet: A Flexible and Extensible Lunar Exploration Communications and 

Navigation Infrastructure,” IEEE Aerospace Conference, Big Sky, MO, 2020

[RD13] Israel, D. et al., “The Benefits of Delay/Disruption Tolerant Networking (DTN) for Future 

NASA Science Missions” Proceedings of the 70th International Astronautical Congress (IAC), 

Washington, DC, October 2019. 

[RD14] Israel, D., Mauldin, K., et al., “LunaNet: A Flexible and Extensible Lunar Exploration 

Communications and Navigation Infrastructure and the Inclusion of SmallSat Platforms,” 34th Annual 

Small Satellite Conference

[RD15] Johnson, S., Vitalpur, S., Tai, W., Schier, J., Bussey, D. B., Bleacher, J. E., “Communications 

Interoperability for Lunar Missions”, 70th International Astronautical Congress (IAC), Washington, 

D. C., October 2019.

[RD16] McCabe, J., and DeMars, K., "Anonymous Feature-Based Terrain Relative Navigation." 

Journal of Guidance, Control, and Dynamics 43.3 (2020): 410-421.

[RD17] Mills, D. et al. Computer Network Time Synchronization: The Network Time Protocol on 

Earth and in Space. CRC press, 2017.

[RD18] Riedel, J. E., et al. "Autonomous Optical Navigation (AutoNav) DS 1 technology validation 

report." Deep Space 1 Technology Validation Reports, Pasadena, CA, Jet Propulsion Laboratory, 

2000.
LNIS V005 August 31, 2023 55

[RD19] Small, J., Mann, L., Crenshaw, J., Gramling, C., Rosales, J., Winternitz, L., Hassouneh, M.,

Baker, D. Hur-Diaz-S., Liounis, A. “Lunar Relay Onboard Navigation Performance and Effects on 

Lander Descent to Surface,” Institute of Navigation International Technical Meeting, January 2022.

[RD20] Valdez, J., Ashman, B., Gramling, C., Heckler, G., “Navigation Architecture for a Space 

Mobile Network,” Proceedings of the 39th American Astronautical Society Guidance and Control 

Conference, Breckenridge, CO, 5-10 February 2016.

[RD21] Wallace, T., InKyu, K., SangMan, M., Day K, Kar-Ming C., “The Lunar Space 

Communications Architecture from the KARI-NASA Joint Study,” AIAA SpaceOps 2016 

Conference, 6 May 2016

[RD22] Winternitz, L., et al. "Global Positioning System Navigation above 76,000Km for NASA's 

Magnetospheric Multiscale Mission." Navigation: Journal of the Institute of Navigation 64.2 (2017): 

289-300.

[RD23] European GNSS (Galileo), Galileo Service Definition Document, issue 1.2, November 2021

[RD24] Radio Frequency and Modulation Systems -Part 1 Earth Stations and Spacecraft, Blue Book, 

Issue 32, CCSDS 401.0-B-32, October 2021.

[RD25] Vilnrotter, V., Hamkins, J., “Telecommand/Telemetry Ranging for Deep Space Applications,” 

IEEE Aerospace Conference, January 14, 2019.
LNIS V005 August 31, 2023 56

APPENDIX A ACRONYMS 

Table A-1 Acronyms 

Acronym Description

3GPP 3rd Generation Partnership Project

AFS Augmented Forward Signal

AOS Advanced Orbiting Systems

ASM Attached Sync Marker

BER Bit Error Rate

BP Bundle Protocol

BPSK Binary Phase Shift Key

CBOR Concise Binary Object Representation

CLPS Commercial Lunar Payload Services

CCSDS Consultative Committee for Space Data Systems

CDMA Code Division Multiple Access

CLTU Command Link Transmission Unit

DEM Digital Elevation Maps

DTE Direct to Earth

DTN Delay/Disruption Tolerant Networking

DWE Direct with Earth

DVB-S2 Digital Video Broadcasting-Second Generation

ECSS Europeans Cooperation for Space Standardization

ESC Exploration and Space Communication

EVA Extravehicular Activity

GMSK Gaussian Minimum Shift Keying

GNSS Global Navigation Satellite System

ICAO International Civil Aviation Organization

ICMP Information and Configuration Management Plan

IETF Internet Engineering Task Force

IMO International Maritime Organization 

IOAG Interagency Operations Advisory Group

IPIOC Internet Protocol

IOC Initial Operational Concept

KSPS Kilo Symbols Per Second 

LANS Lunar Augmented Navigation System

LDPC Low Density Parity Check

LNSP LunaNet Service Providers

LTP Licklider Transmission Protocol

MAR Multiple-Access-Return

MHZ Megahertz

MOC Mission Operations Center

NPD NASA Policy Directives 
LNIS V005 August 31, 2023 57

Acronym Description

NPR NASA Procedural Requirements

NRZ-L Nonreturn-To-Zero Level

NTP Netrix Trunk Protocol

OQPSK Offset Quadrature Phase Shift Keying

P2P Point to Point

PN Pseudo-Noise

PNT Position, Navigation, and Timing

PVT Position, Velocity, and Timing

RD Reference Document

RF Radio Frequency

RFC Radio Frequency Compatibility

RHCP Right-Hand Circularly Polarized

SAR Search and Rescue

SCaN Space Communications and Navigation

SCCC Spacecraft Command and Control Center

SFCG Space Frequency Coordination Group

SS-BPSK Spread Spectrum Binary Phase-Shift Keying 

TBD To Be Determined

TBR To Be Refined

TCP/IP Transmission Control Protocol/Internet Protocol

UDP User Datagram Protocol

VCM Variable Coding and Modulation

Wi-Fi Wireless Fidelity
LNIS V005 August 31, 2023 58

APPENDIX B SIGNAL INTERFACE DESCRIPTIONS

B.I LNSP-USER PROXIMITY INTERFACES

This section defines the specifications for the signal formats across proximity links between LNSPs and 

users. The following general notes apply to the LNSP-User proximity interfaces:

A. An adaptation of Proximity-1 protocols for the use of lunar missions in S-Band and K-band is 

currently under consideration and will be evaluated based on spectrum and other technical 

considerations. Reference CCSDS 211.0-B-6, CCSDS 211.1-B-4, and CCSDS 211.2-B-3. 

Further details will be disseminated in future LunaNet specification releases.

B. In order to ease acquisition tracking in the presence of large Doppler dynamics, Doppler 

compensation could be used. As a specific example, for users with very low signal strength that 

require very narrow bandwidths, Doppler compensation might be required.

C. When using shaped pulses (e.g., filtered OQPSK, GMSK+PN) at the lower limits of the data rate 

range, bit error rate (BER) degradation and/or synchronization issues can occur. At low data rates, 

the normalized loop bandwidth (loop bandwidth normalized to data rate) increases, which can 

result in BER degradation of the signal. Increasing the normalized loop bandwidth can allow for 

cycle slips in the tracking loop, which could result in link stability issues and can also degrade 

BER performance. The tracking loop bandwidth must be large enough to accommodate the link 

doppler rates, which is dependent on the specific geometry of each relay/user link. Developers 

and mission planners should ensure through hardware testing that the receiver can properly 

operate at the low data rates for the worst-case doppler scenarios that a specific user to relay (and 

relay to user) link will see.

D. Low-Density Parity Check (LDPC) codes are shown here in parenthetical (n, k) format, where n 

is the codeword length in bits and k is the information block length in bits. The code rate is also 

shown, although this can also be derived by rr = kk/nn. CCSDS 131.0-b Section 7.3 describes the 

LDPC 7/8 (8160, 7136) code. CCSDS 231.0-b Section 4 describes the LDPC 1⁄2 (128, 64) and 

LDPC 1/2 (512, 256) codes. CCSDS 131.0-b Section 7.4 describes the remaining LDPC 1⁄2, LDPC 

2/3, and LDPC 4/5 of various (n, k) values used in this specification. CCSDS 131.0-b Section 8 

describes how slicing can be used to use LDPC codes with transfer frames up to the CCSDS limit 

(currently 524,288 bits for USLP and 16,384 bits for AOS) using slicing.

E. LunaNet proximity services should be available on both Left-Hand Circularly Polarized (LHCP) 

and Right-Hand Circularly Polarized (RHCP) waveforms to use spectrum allocations most 

efficiently. It is therefore recommended that LNSP relay vehicles be capable of switching to either 

polarization, or capable of providing simultaneous service on both polarizations (e.g., dual 

polarization). Some user missions may choose to operate with dual polarization, although that 

scenario is not explicitly discussed in this specification. The AFS service (PFS5) operates on a 

single polarization as defined in [AD1]. The MAR signal service (PRS5) has not been fully 

defined, including polarization.

B.I.I SINGLE ACCESS LNSP-USER PROXIMITY INTERFACES

The following notes apply to particular Single Access LNSP-User Proximity signal formats, with the 

notes referred to in the signal specifications in the following subsections.

[1] S-band is primarily intended for tracking, telemetry, and command (TT&C) data. The standard 

maximum bandwidth for non-spread spectrum S-band signals is limited to up to 5 MHz to allow 

systems to operate efficiently, and the maximum symbol and chip rates specifications are made 

in accordance with this standard limitation. In the interest of interoperability, all LNSPs should 

be capable of meeting the rate and subcarrier ranges specified here. However, this specification 

does not prohibit users from requesting wider bandwidths and capabilities beyond these ranges, 

assuming that they can acquire spectrum authorization and find service providers capable of the 

requested service. 
LNIS V005 August 31, 2023 59

[2] NRZ-L should be used for code symbols unless explicitly stated otherwise. NRZ-L is selected 

as the use of differential encoding (e.g., NRZ-M) would double decoding errors (one wrong 

level leads to two wrong transitions). See CCSDS 401-B Sections 2.4.2 and 2.4.11.

[3] Filtering is typical and recommended for BPSK signals. Users may choose to not filter BPSK 

signals in some situations, and LNSPs should be capable of accommodating that request. As a 

minimum for interoperability, LNSPs should have the capability to provide root raised cosine 

filtering. Users should understand that when choosing other filtering options, there may be 

increased losses due to unmatched filtering. LNSPs may choose to implement additional 

filtering types for user flexibility.

[4] See CCSDS 131.0-B- Section 7.4 for LDPC 1/2, 2/3, and 4/5.

[5] See CCSDS 131.0-B- Section 7.3 for LDPC 7/8.

[6] LDPC codes can be used with transfer frames up to the CCSDS limit (currently 524,288 bits 

for USLP and 16,384 bits for AOS) using slicing.

[7] All transfer frames shall be either AOS or USLP.

[8] The most recent version of the applicable standard shall be used, unless stated otherwise.

[9] PCM/PM (PFS1b/PRS1b) can also be supported with NRZ-L data format. It is expected that 

LNSPs should offer this capability, and the choice is left to users whether to utilize Bi-PhaseL or NRZ-L. Note that use of NRZ-L for this modulation is not currently discussed in CCSDS 

401.0-B.

[10] The modulation index ranges provided here are a recommendation to ensure minimum 

interoperability of LNSPs. Users may request modulation index ranges outside this range, 

assuming they can get appropriate approvals and find an LNSP with the capability to service 

them.

[11] The use of simultaneous ranging with data requires consideration on the interaction between 

the carrier, data signal, and ranging signal. The ECSS Radio Frequency and Modulation 

handbook, ECSS-E-ST-50-05C Rev 2 Section 6.1.6 provides a useful rule-of-thumb: the 

combined peak modulation index (sum of data and ranging modulation indices) should not 

exceed 1.75 radians. The LunaNet interoperability specification does not prohibit violation of 

this rule, but it is strongly recommended to consider the performance of simultaneous ranging 

and data transmission in such circumstances.

[12] Applicable documents for some signals are to be determined. Standards development and 

coordination for lunar proximity communications is an ongoing effort. Future coordination with 

CCSDS to clarify these applications is planned.

[13] Several of the CCSDS recommendations within this section are currently written regarding 

Space-to-Earth and Earth-to-Space links. Despite the use of Earth focused language in the 

existing standards, these standards are applicable to the LunaNet specifications where cited.

[14] In some cases, the CCSDS standard specifically refer to usage for telemetry or telecommand 

but not both. The LunaNet specifications are symmetric in the return and forward directions, 

and therefore sometimes apply telemetry standards to telecommand links and vice-versa. This 

discrepancy between CCSDS recommendations and LunaNet specifications is realized and 

future clarification in coordination with CCSDS will be provided. 

[15] For high throughput K-band links, higher order modulations and coding schemes are 

recommended to maximize bandwidth efficiency. Bandwidth efficient modulation and coding 

schemes are being investigated for LunaNet implementation.
LNIS V005 August 31, 2023 60

Table B-1: PFS1a - Proximity Forward S-Band Data Only

PFS1a - Proximity Forward S-Band Data Only

Parameter Description Notes

Frequency Range 2025-2110 MHz See CCSDS 401.0-B Section 2.2.8 and 2.3.2 for 

explanation of BPSK.

[1] [2] [3] 

Polarization LHCP and/or RHCP

Symbol Rate 2 ksps ≤ Rs ≤ 2.048 Msps

Modulation Filtered BPSK 

Radiometric Ranging 

Options

No -

Coding and Framing Symbol Rate 0.002 to 1.0Msps

• LDPC r=1⁄2 (2048, 1024)

• Uncoded, Message Size 16,384 

bits

Symbol Rate 1.0 to 2.0 Msps

• LDPC 1/2 (32768, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

• Uncoded, Message Size 16,384 

bits

[4] [5] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B

[8]

Table B-2: PFS1b - Proximity Forward S-Band Medium Rate w/ Ranging

PFS1b - Proximity Forward S-Band Medium Rate w/ Ranging

Parameter Description Notes

Frequency Range 2025-2110 MHz Presence of residual carrier aids demodulation 

(e.g., large doppler dynamics scenarios) and 

allows simultaneous ranging.

See CCSDS 401.0-B Section 2.2.7 for 

explanation of PCM/PM/bi-phase-L.

[1] [9] [10] [11]

Polarization LHCP and/or RHCP

Symbol Rate 48 ksps ≤ Rs ≤ 1.024 Msps

Modulation PCM/PM/bi-phase-L

Data Modulation Index: 0.2 to 1.4 

radians (peak) 

Radiometric Ranging 

Options

PN Ranging

Ranging Modulation Index: 0.2 to 1.4 

radians (peak) 

Chip rate: up to 2.3 Mcps

Coding and Framing • LDPC 1⁄2 (2048, 1024)

• LDPC 2/3 (6144, 4096)

• Convolutional, r=1/2, k=7

• Uncoded, Message Size 16,384 

bits [TBD]

[4] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 414.1-B

[8] [12]
LNIS V005 August 31, 2023 61

Table B-3: PFS1c - Proximity Forward S-Band Low-Rate w/ Ranging 

PFS1c - Proximity Forward S-Band Low-Rate w/ Ranging 

Parameter Description Notes

Frequency Range 2025-2110 MHz Presence of residual carrier aids demodulation 

(e.g., large doppler dynamics scenarios) and 

allows simultaneous ranging.

See CCSDS 401.0-B Section 2.2.4 for 

explanation of PCM/PSK/PM.

[1] [10] [11] 

Polarization LHCP and/or RHCP

Symbol Rate 0.5 ksps ≤ Rs ≤ 48 ksps

Subcarrier Freq. (Sine):

4*Rs (or 8 kHz minimum)

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index: 0.2 to 1.8 

radians (peak) 

Radiometric Ranging 

Options

PN Ranging on carrier

Ranging Modulation Index: 0.2 to 1.4 

radians (peak) 

Chip rate: up to 2.3 Mcps

Coding and Framing • LDPC 1⁄2 (2048, 1024) [4] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 414.1-B

[8] [12]

Table B-4: PFS1d - Proximity Forward S-Band High-Rate Data Only

PFS1d - Proximity Forward S-Band High-Rate Data Only 

Parameter Description Notes

Frequency Range 2025-2110 MHz See CCSDS 401.0-B- Section 2.4.17A for 

explanation of Filtered OQPSK and GMSK.

This signal allows higher data rates with 

bandwidth efficiency.

[1] [13] [14] 

Polarization LHCP and/or RHCP

Symbol Rate 1 Msps ≤ Rs ≤ 5 Msps

Modulation Filtered OQPSK or GMSK 

Radiometric Ranging 

Options

No

Coding and Framing • LDPC 1⁄2 (2048, 1024)

• LDPC 1⁄2 (8192, 4096)

• LDPC 2/3 (6144, 4096)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

• Convolutional, r=1⁄2, k=7

• Uncoded, Message Size 16,384 

bits [TBD] 

[4] [5] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B

[8] [12]
LNIS V005 August 31, 2023 62

Table B-5: PFS1e - Proximity Forward S-Band High-Rate w/ Ranging

PFS1e - Proximity Forward S-Band High-Rate w/ Ranging

Parameter Description Notes

Frequency Range 2025-2110 MHz See CCSDS 401.0-B- Section 2.4.22A for an 

explanation of GMSK+PN. 

To be recommended for S-band Lunar 

Proximity.

Allows bandwidth efficient higher data rates with 

simultaneous ranging

[1] [13] [14]

Polarization LHCP and/or RHCP

Symbol Rate 1 Msps ≤ Rs ≤ 5 Msps

Modulation GMSK+PN Ranging

Radiometric Ranging 

Options

Yes

Coding and Framing • LDPC 1⁄2 (2048, 1024)

• LDPC 1⁄2 (8192, 4096)

• LDPC 2/3 (6144, 4096)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

[4] [5] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B

[8] [12]

Table B-6: PRS1a - Proximity Return S-Band Data Only

PRS1a - Proximity Return S-Band Data Only

Parameter Description Notes

Frequency Range 2200-2290 MHz See CCSDS 401.0-B Section 2.3.2 for 

explanation of BPSK.

[1] [2] [3] [13] 

Polarization LHCP and/or RHCP

Symbol Rate 2 ksps ≤ Rs ≤ 2.048 Msps

Modulation Filtered BPSK 

Radiometric Ranging 

Options

No -

Coding and Framing Symbol Rate 0.002 to 1.0Msps

• LDPC r=1⁄2 (2048, 1024)

• Uncoded, Message Size 16,384 

bits

Symbol Rate 1.0 to 2.0 Msps

• LDPC 1⁄2 (32768, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

• Uncoded, Message Size 16,384 

bits

[4] [5] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B

[8]
LNIS V005 August 31, 2023 63

Table B-7: PRS1b - Proximity Return S-Band Medium Rate w/ Ranging

PRS1b - Proximity Return S-Band Medium Rate w/ Ranging

Parameter Description Notes

Frequency Range 2200-2290 MHz Presence of residual carrier aids demodulation 

(e.g., large doppler dynamics scenarios) and 

allows simultaneous ranging.

See CCSDS 401.0-B Sections 2.4.7 and 2.4.15A 

for explanation of PCM/PM/bi-phase-L.

[1] [9] [10] [11] [13] [14]

Polarization LHCP and/or RHCP

Symbol Rate 48 ksps ≤ Rs ≤ 1.024 Msps

Modulation PCM/PM/bi-phase-L

Data Modulation Index: 0.2 to 1.4 

radians (peak) 

Radiometric Ranging 

Options

PN Ranging

Ranging Modulation Index: 0.2 to 1.0 

radians (peak) 

Chip rate: up to 2.3 Mcps

Coding and Framing • LDPC 1⁄2 (2048, 1024)

• LDPC 2/3 (6144, 4096)

• Convolutional, r=1⁄2, k=7

• Uncoded, Message Size 16,384 

bits [TBD]

[4] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 414.1-B

[8] [12]

Table B-8: PRS1c - Proximity Return S-Band Low-Rate w/ Ranging

PRS1c - Proximity Return S-Band Low-Rate w/ Ranging 

Parameter Description Notes

Frequency Range 2200-2290 MHz Presence of residual carrier aids demodulation 

(e.g., large doppler dynamics scenarios) and 

allows simultaneous ranging.

See CCSDS 401.0-B Sections 2.2.4, 2.4.3, and 

2.4.7 for explanation of PCM/PSK/PM. 

[1] [10] [11] [13] [14]

Polarization LHCP and/or RHCP

Symbol Rate 0.5 ksps ≤ Rs ≤ 48 ksps

Subcarrier Freq. (Sine):

4*Rs (or 8 kHz minimum)

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index: 0.2 to 1.8 

radians (peak) 

Radiometric Ranging 

Options

PN Ranging on carrier

Ranging Modulation Index: 0.2 to 1.0 

radians (peak) 

Chip rate: up to 2.3 Mcps

Coding and Framing • LDPC 1⁄2 (2048, 1024) [4] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 414.1-B

[8] [12]
LNIS V005 August 31, 2023 64

Table B-9: PRS1d - Proximity Return S-Band High-Rate Data Only 

PRS1d - Proximity Return S-Band High-Rate Data Only

Parameter Description Notes

Frequency Range 2200-2290 MHz See CCSDS 401.0-B- Section 2.4.17A for 

explanation of Filtered OQPSK and GMSK.

Allows for higher data rates with bandwidth 

efficiency.

[1] [13]

Polarization LHCP and/or RHCP

Symbol Rate 1 Msps ≤ Rs ≤ 5 Msps

Modulation Filtered OQPSK or GMSK 

Radiometric Ranging 

Options

No

Coding and Framing • LDPC 1⁄2 (2048, 1024)

• LDPC 1⁄2 (8192, 4096)

• LDPC 2/3 (6144, 4096)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

• Convolutional, r=1⁄2, k=7

• Uncoded, Message Size 16,384 

bits [LNIS-TBR-4012]

[4] [5] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B

[8] [12] 

Table B-10: PRS1e - Proximity Return S-Band High-Rate w/ Ranging 

PRS1e - Proximity Return S-Band High-Rate w/ Ranging

Parameter Description Notes

Frequency Range 2200-2290 MHz See CCSDS 401.0-B Section 2.4.22A for an 

explanation of GMSK+PN. 

To be recommended for S-band Lunar 

Proximity.

Allows bandwidth efficiency higher data rates 

with simultaneous ranging

[1] [13] 

Polarization LHCP and/or RHCP

Symbol Rate 1 Msps ≤ Rs ≤ 5 Msps

Modulation GMSK+PN Ranging

Radiometric Ranging 

Options

Yes

Coding and Framing • LDPC 1⁄2 (2048, 1024)

• LDPC 1⁄2 (8192, 4096)

• LDPC 2/3 (6144, 4096)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

[4] [5] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B

[8] [12]
LNIS V005 August 31, 2023 65

Table B-11: PFK1 - Proximity Forward K-band Data Only 

PFK1 - Proximity Forward K-band Data Only 

Parameter Description Notes

Frequency Range 23.15-23.55 GHz See CCSDS 401.0-B Section 2.3.2 for 

explanation of BPSK.

Allows a simplified forward service on K-band 

for needs not requiring very high data rates. 

[13] [14]

Polarization LHCP and/or RHCP

Symbol Rate 1 Msps ≤ Rs ≤ 2.048 Msps {TBR}

Modulation BPSK 

Radiometric Ranging 

Options

No

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 2/3 (24576, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

• Uncoded, Message Size 16,384 

bits

[4] [5] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B [8]

Table B-12: PFK2 - Proximity Forward K-band Variable Coding and Modulation

PFK2 - Proximity Forward K-band Variable Coding and Modulation

Parameter Description Notes

Frequency Range 23.15-23.55 GHz See CCSDS 401.0-B Section 2.4.23 and CCSDS 

431.1-B for explanation of DVB-S1 and SCCC 

VCM methods. 

LDPC-VCM is not yet a formal CCSDS 

standard.

Allows high data throughputs with spectrally 

efficient VCM schemes.

[13] [14] [15] 

Polarization LHCP and/or RHCP

Symbol Rate 1 Msps ≤ Rs ≤ {TBD} Msps 

Modulation DVB-S2 or SCCC or LDPC-VCM

Radiometric Ranging 

Options

No

Coding and Framing TBD -

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 131.3-B 

CCSDS 431.1-B 

CCSDS 131.2-B

[8]
LNIS V005 August 31, 2023 66

Table B-13: PFK3 - Proximity Forward K-band High-Rate Data Only 

PFK3 - Proximity Forward K-band High-Rate Data Only

Parameter Description Notes

Frequency Range 23.15-23.55 GHz See CCSDS 401.0-B Section 2.4.21A for 

explanation of Filtered OQPSK and GMSK.

Allows spectrally efficient high data 

throughputs with simpler implementation than 

VCM.

[13] [14] [15] 

Polarization LHCP and/or RHCP

Symbol Rate 1 Msps ≤ Rs ≤ {TBD}Msps

Modulation Filtered OQPSK or GMSK

Radiometric Ranging 

Options

No

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 2/3 (24576, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

• Uncoded, Message Size 16,384 

bits

[4] [5] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B

[8]

Table B-14: PFK4 - Proximity Forward K-band High-Rate Data w/ Ranging 

PFK4 - Proximity Forward K-band High-Rate Data w/ Ranging 

Parameter Description Notes

Frequency Range 23.15-23.55 GHz See CCSDS 401.0-B- Section 2.4.22A for 

explanation of GMSK+PN.

To be recommended for K-band Lunar 

Proximity.

Allows simultaneous ranging on K-band 

signals.

[10] [11] [13] [14] [15] 

Polarization LHCP and/or RHCP

Symbol Rate 1.5 Msps ≤ Rs ≤ {TBD} Msps

Modulation GMSK+PN

Radiometric Ranging 

Options

Yes

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 2/3 (24576, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

• Uncoded, Message Size 16,384 

bits

[4] [5] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B

[8]
LNIS V005 August 31, 2023 67

Table B-15: PRK1 - Proximity Return K-band Data Only 

PRK1 - Proximity Return K-band Data Only 

Parameter Description Notes

Frequency Range 27.0-27.5 GHz See CCSDS 401.0-B Section 2.3.2 for 

explanation of BPSK.

Allows a simplified return service on K-band 

for needs not requiring very high data rates.

[13] [15]

Polarization LHCP and/or RHCP

Symbol Rate 1 Msps ≤ Rs ≤ 2.048 Msps

Modulation BPSK 

Radiometric Ranging 

Options

No

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 2/3 (24576, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

• Uncoded, Message Size 16,384 

bits

[4][5][6][7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B [8]

Table B-16: PRK2 - Proximity Return K-band Variable Coding and Modulation

PRK2 - Proximity Return K-band Variable Coding and Modulation

Parameter Description Notes

Frequency Range 27.0-27.5 GHz See CCSDS 401.0-B Section 2.4.23 and CCSDS 

431.1-B for explanation of DVB-S1 and SCCC 

VCM methods. 

LDPC-VCM is not yet a formal CCSDS 

standard.

Allows high data throughputs with spectrally 

efficient VCM schemes.

[13] [14] [15] 

Polarization LHCP and/or RHCP

Symbol Rate 1 Msps ≤ Rs ≤ {TBD} Msps 

Modulation DVB-S2 or SCCC or LDPC-VCM

Radiometric Ranging 

Options

No

Coding and Framing TBD -

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 131.3-B 

CCSDS 431.1-R 

CCSDS 131.2-B

[8]
LNIS V005 August 31, 2023 68

Table B-17: PRK3 - Proximity Return K-band High-Rate Data Only 

PRK3 - Proximity Return K-band High-Rate Data Only 

Parameter Description Notes

Frequency Range 27.0-27.5 GHz See CCSDS 401.0-B Section 2.4.17A.

Allows spectrally efficient high data 

throughputs with simpler implementation than 

VCM.

[13] [15]

Polarization LHCP and/or RHCP

Symbol Rate 1 Msps ≤ Rs ≤ {TBD}Msps

Modulation Filtered OQPSK or GMSK

Radiometric Ranging 

Options

No

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 2/3 (24576, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

• Uncoded, Message Size 16,384 

bits

[4] [5] [6] [7] 

Applicable 

Documents

CCSDS 131.0-B

CCSDS 401.0-B

[8] 

Table B-18: PRK4 - Proximity Return K-band High-Rate Data w/ Ranging 

PRK4 - Proximity Return K-band High-Rate Data w/ Ranging 

Parameter Description Notes

Frequency Range 27.0-27.5 GHz See CCSDS 401.0-B- Section 2.4.22A for 

explanation of GMSK+PN.

To be recommended for K-band Lunar 

Proximity.

Allows simultaneous ranging on K-band 

signals.

[13] [14] [15]

Polarization LHCP and/or RHCP

Symbol Rate 1.5 Msps ≤ Rs ≤ {TBD} Msps

Modulation GMSK+PN

Radiometric Ranging 

Options

Yes

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 2/3 (24576, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

• Uncoded, Message Size 16,384 

bits

[4] [5] [6] [7]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B

[8]
LNIS V005 August 31, 2023 69

B.I.IISPREAD SPECTRUM LNSP-USER PROXIMITY INTERFACES

The following general notes regard the development of the spread spectrum signals:

A. The option to use non-regenerative ranging in the 415.1-B book has been proposed and is being 

worked on at CCSDS. 

B. The intent of unbalanced return in the 415.1-B book was for higher science return data rate on one 

channel. These concepts are superseded by CCSDS virtual channels, where data rates of telemetry 

and science are controlled by the frame rates of the channels. Single data channel balanced QPSK 

is recommended for the lunar proximity return links.

The following notes apply to particular spread spectrum LNSP-user proximity link signal formats, with 

the notes referred to in the signal specifications in the following subsections:

[1] Standard maximum bandwidth for spread spectrum S-band signal is 6.16 MHz. This allows a chip 

rate of ~3 Mcps.

[2] See CCSDS 131.0-B Section 7.4 for LDPC 1/2, 2/3, and 4/5.

[3] LDPC codes can be used with transfer frames up to the CCSDS limit (currently 524,288 bits for 

USLP and 16,384 bits for AOS) using slicing.

[4] All transfer frames shall be either AOS or USLP

[5] The most recent version of the applicable standard shall be used, unless stated otherwise.

[6] Applicable documents for some signals are to be determined. Standards development and 

coordination for lunar proximity communications is an ongoing effort. Future coordination with 

CCSDS to clarify these applications is planned.
LNIS V005 August 31, 2023 70

Table B-19: PFS2 - Proximity Forward S-band Medium Rate w/ Ranging

PFS2 - Proximity Forward S-band Medium Rate w/ Ranging 

Parameter Description Notes

Frequency Range 2025-2110 MHz

Fixed frequency assignments are 

{TBD}

The intent of this signal is a medium data rate signal 

with spread spectrum PN ranging and user specific PN 

code. Differentiated from PFS5 in that PFS5 utilizes a 

relay specific PN code for navigation service. Allows 

for higher data rates than PFS5, and signal parameters 

could be modified to some extent for individual users.

[1]

Polarization LHCP and/or RHCP

Symbol Rate Symbol & Chip Rates are {TBD}

Modulation SS-BPSK CDMA

(~3Mcps) 

or 

SS-UQPSK {TBD}

Radiometric Ranging 

Options

Yes, details are {TBD}

Coding and Framing LDPC 1⁄2 (2048, 1024) [2][3][4]

Applicable 

Documents

CCSDS 415.1-B

CCSDS 131.0-B [5][6]

Table B-20: PRS2 - Proximity Return S-Band Spread Spectrum 

PRS2 - Proximity Return S-Band Spread Spectrum 

Parameter Description Notes

Frequency Range 2200-2290 MHz

Fixed frequency assignments are 

{TBD}

Intent is for a wide beam spread spectrum return 

intended for P2P links. Similar to PRS5 but allows for 

higher data rates (less spreading) and ranging. There is 

a possibility to support multiple users simultaneously, 

albeit much less than PRS5. Signal parameters could 

also be modified for user specific needs {TBR}.

[1]

Polarization LHCP and/or RHCP

Symbol Rate Symbol & Chip Rates are {TBD}

Modulation SS-BPSK CDMA

(~3Mcps) 

or 

SS-UQPSK {TBD}

Radiometric Ranging 

Options

Yes, details are {TBD}

Coding and Framing LDPC 1⁄2 (2048, 1024) [2] [3] [4] 

Applicable 

Documents

CCSDS 415.1-B 

CCSDS 131.0-B

[5] [6]
LNIS V005 August 31, 2023 71

Table B-21: PFS5 - Proximity Forward S-band Augmented Forward Signal (AFS) 

Augmented Forward Signal (AFS) - PFS5 - Proximity Forward S-band 

Parameter Description Notes

Frequency Range 2483.5-2500 MHz, Fc = 2492.028 

MHz

See Lunar Augmented Navigation System (LANS)

Symbol Rate AFS Structure (Appendix C)

Modulation AFS Structure (Appendix C)

Radiometric Ranging 

Options

Yes

Coding and Framing AFS Structure (Appendix C)

Applicable 

Documents

AFS Structure (Appendix C)

Table B-22: PRS5 - Proximity Return S-Band Multiple Access Return (MAR) 

Multiple Access Return (MAR) - PRS5 - Proximity Return S-Band 

Parameter Description Notes

Frequency Range 2200-2290 MHz

Fixed frequency assignments are 

{TBD}

Low rate, many users multiple access return with 

ranging. 

[1]

Polarization {TBD}

Symbol Rate Symbol & Chip Rates are {TBD}

Modulation SS-BPSK CDMA

(~3Mcps) 

or 

SS-UQPSK {TBD}

Radiometric Ranging 

Options

Yes, details are {TBD}

Coding and Framing TBD [4]

Applicable 

Documents

CCSDS 415.1-B

CCSDS 131.0-B

[5]
LNIS V005 August 31, 2023 72

B.II LNSP – USER DWE INTERFACES

This section provides a summary of the signal definitions for the DWE links. DWE applies both to direct 

links between Earth and lunar surface and links between Earth and LunaNet relay nodes. In this document 

the special case of the link between a lunar relay orbiter and Earth station is identified as the “trunk link.” 

A trunk link exists in both the forward and return directions.

The following general notes apply to DWE signals:

A. It is recommended that LNSPs and users utilize both Left-Hand Circularly Polarized (LHCP) and 

Right-Hand Circularly Polarized (RHCP) waveforms to use DWE spectrum allocations most 

efficiently. LNSPs and users should consider making DWE systems with switchable polarization, 

or dual polarization (utilizing both polarizations simultaneously to maximize efficiency). 

B. Low-Density Parity Check (LDPC) codes are shown here in parenthetical (n, k) format, where n is 

the codeword length in bits and k is the information block length in bits. The code rate is also 

shown, although this can also be derived by rr = kk/nn. CCSDS 131.0-b Section 7.3 describes the 

LDPC 7/8 (8160, 7136) code. CCSDS 231.0-b Section 4 describes the LDPC 1⁄2 (128, 64) and 

LDPC 1⁄2 (512, 256) codes. CCSDS 131.0-b Section 7.4 describes the remaining LDPC 1⁄2, LDPC 

2/3, and LDPC 4/5 of various (n, k) values used in this specification. CCSDS 131.0-b Section 8 

described how slicing can be used to use LDPC codes with transfer frames up to the CCSDS limit 

(currently 524,288 bits for USLP and 16,384 bits for AOS) using slicing.

The following notes apply to particular DWE link signal formats, with the notes referred to in the signal 

specifications in the following subsections:

[1] PCM/PM (XU1/XD1) can also be supported with NRZ-L data format. It is expected that LNSPs 

should offer this capability, and the choice is left to users whether to utilize Bi-Phase-L or NRZ-L. 

Note that use of NRZ-L for this modulation is not currently discussed in CCSDS 401.0-B.

[2] The modulation index ranges provided here are a recommendation to ensure minimum 

interoperability of LNSPs. Users may request modulation index ranges outside this range, assuming 

they can get appropriate approvals and find an LNSP with the capability to service them.

[3] The use of simultaneous ranging with data requires consideration on the interaction between the 

carrier, data signal, and ranging signal. The ECSS Radio Frequency and Modulation handbook, 

ECSS-E-ST-50-05C Rev 2 Section 6.1.6 provides a useful rule-of-thumb: the combined peak 

modulation index (sum of data and ranging modulation indices) should not exceed 1.75 radians. 

This interoperability specification does not prohibit violation of this rule, but it is strongly 

recommended to consider the performance of simultaneous ranging and data transmission in such 

circumstances.

[4] The 4 Mcps chip rate is based on the standard maximum allowed bandwidth of 10 MHz for X-band 

Space Research.

[5] See CCSDS 231.0-B – for description of LDPC short codes (128, 64) & (512, 256).

[6] See CCSDS 131.0-B- Section 7.4 for a description of LDPC 1/2, 2/3, and 4/5.

[7] See CCSDS 131.0-B- Section 7.3 for a description of LDPC 7/8.

[8] LDPC codes can be used with transfer frames up to the CCSDS limit (currently 524,288 bits for 

USLP, 16,384 bits for AOS) using slicing. See CCSDS 131.0-B- Chapter 8 and Chapter 11.

[9] All transfer frames shall be either AOS or USLP.

[10] The most recent version of the applicable standard shall be used, unless stated otherwise.
LNIS V005 August 31, 2023 73

[11] Applicable documents for some signals are to be determined. Standards development and 

coordination for lunar proximity communications is an ongoing effort. Future coordination with 

CCSDS to clarify these applications is planned. In some cases, the CCSDS standard specifically 

refer to usage for telemetry or telecommand but not both. The LunaNet specifications are 

symmetric in the return and forward directions, and therefore sometimes apply telemetry standards 

to telecommand links and vice-versa. This discrepancy between CCSDS recommendations and 

LunaNet specifications is realized and future clarification in coordination with CCSDS will be 

provided. 

[12] For high throughput K-band trunk links (> 200 Msps), higher order modulations and coding 

schemes are recommended to maximize bandwidth efficiency. VCM or a subset of the codes in 

the VCM standard can be considered.
LNIS V005 August 31, 2023 74

Table B-23: XU1 - X-band Uplink Medium Rate w/ Ranging

XU1 - X-band Uplink Medium Rate w/ Ranging 

Parameter Description Notes

Frequency Range 7190-7235 MHz See CCSDS 401.0-B Section 2.2.7 for 

explanation of PCM/PM/bi-phase-L.

Presence of residual carrier aids demodulation 

(e.g., large doppler dynamics scenarios) and 

allows simultaneous ranging.

[1] [2] [3] [4] 

Polarization LHCP and/or RHCP

Symbol Rate 64 ksps ≤ Rs ≤ 1.024 Msps

Modulation PCM/PM/bi-phase-L

Data Modulation Index: 0.2 to 1.4 

radians (Peak)

Radiometric Ranging 

Options

PN Ranging

Ranging Modulation Index: 0.2 to 

1.4 radians (Peak)

Chip rate: up to 4 Mcps 

Coding and Framing • LDPC 1⁄2 (512, 256)

• LDPC 1⁄2 (32768, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

[5] [6] [7] [8] [9]

Applicable Documents CCSDS 131.0-B

CCSDS 231.0-B 

CCSDS 401.0-B 

CCSDS 414.1-B

[10]

Table B-24: XU2 - X-band Uplink High-Rate w/ Ranging

 

XU2 - X-band Uplink High-Rate w/ Ranging 

Parameter Description Notes

Frequency Range 7190-7235 MHz See CCSDS 401.0-B- Section 2.4.22A for an 

explanation of GMSK+PN

Allows bandwidth efficient higher data rates with 

simultaneous ranging.

Polarization LHCP and/or RHCP

Symbol Rate 150 ksps ≤ Rs ≤ 1 Msps

Modulation GMSK+PN

Radiometric Ranging 

Options

Yes

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

[6] [7] [8] [9]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 414.1-B

[10] [11]
LNIS V005 August 31, 2023 75

Table B-25: XU3 - X-band Uplink Low-Rate w/ Ranging

XU3 - X-band Uplink Low-Rate w/ Ranging

Parameter Description Notes

Frequency Range 7190-7235 MHz See CCSDS 401.0-B Section 2.2.4 for 

explanation of PCM/PSK/PM. 

Presence of residual carrier aids demodulation 

(e.g., large doppler dynamics scenarios) and 

allows simultaneous ranging.

[2] [3] [4]

. 

Polarization LHCP and/or RHCP

Symbol Rate 0.5 ksps ≤ Rs ≤ 64 ksps

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index:

0.2 to 1.8 radians (Peak)

Radiometric Ranging 

Options

PN Ranging

Ranging Modulation Index: 0.2 to 

1.4 radians (Peak)

Chip rate: up to 4 Mcps

Coding and Framing • LDPC 1⁄2 (512, 256)

• LDPC 1⁄2 (2048, 1024)

• Uncoded, Message Size 

16,384 bits

[5] [6] [8] [9]

Applicable Documents CCSDS 131.0-B

CCSDS 231.0-B 

CCSDS 401.0-B 

CCSDS 414.1-B

[10]

Table B-26: XU4 - X-band Uplink High-Rate Data Only

XU4 - X-band Uplink High-Rate Data Only

Parameter Description Notes

Frequency Range 7190-7235 MHz See CCSDS 401.0-B- Section 2.4.17A for 

explanation of Filtered OQPSK and GMSK.

Allows for higher data rates with bandwidth 

efficiency.

Polarization LHCP and/or RHCP

Symbol Rate 128 ksps ≤ Rs ≤ 10 Msps

Modulation Filtered OQPSK or GMSK

Radiometric Ranging 

Options

No

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

[6] [7] [8] [9] 

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B [10] [11]
LNIS V005 August 31, 2023 76

Table B-27: XD1 - X-band Downlink Medium Rate w/ Ranging 

XD1 - X-band Downlink Medium Rate w/ Ranging 

Parameter Description Notes

Frequency Range 8450-8500 MHz See CCSDS 401.0-B Sections 2.2.7 and 2.4.7 

for explanation of PCM/PM/bi-phase-L 

Presence of residual carrier aids demodulation 

(e.g., large doppler dynamics scenarios) and 

allows simultaneous ranging.

[1] [2] [3] [4]

Polarization LHCP and/or RHCP

Symbol Rate 64 ksps ≤ Rs ≤ 1.024 Msps

Modulation PCM/PM/bi-phase-L

Data Modulation Index: 0.2 to 1.4 

radians (Peak) 

Radiometric Ranging 

Options

PN Ranging

Ranging Modulation Index: 0.2 to 

1.0 radians (Peak)

Chip rate: up to 4 Mcps

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

[6] [7] [8] [9]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 414.1-B

[10] [11] 

Table B-28: XD2 - X-band Downlink High-Rate w/ Ranging 

XD2 - X-band Downlink High-Rate w/ Ranging 

Parameter Description Notes

Frequency Range 8450-8500 MHz See CCSDS 401.0-B- Section 2.4.22A for an 

explanation of GMSK+PN

Allows bandwidth efficient higher data rates with 

simultaneous ranging.

Polarization LHCP and/or RHCP

Symbol Rate 150 ksps ≤ Rs ≤ 1 Msps

Modulation GMSK+PN

Radiometric Ranging 

Options

Yes

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

[6] [7] [8] [9] 

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 414.1-B

[10] [11]
LNIS V005 August 31, 2023 77

Table B-29: XD3 - X-band Downlink Low-Rate w/ Ranging 

XD3 - X-band Downlink Low-Rate w/ Ranging 

Parameter Description Notes

Frequency Range 8450-8500 MHz See CCSDS 401.0-B Sections 2.2.4, 2.4.3, and 2.4.7 

for explanation of PCM/PSK/PM.

Presence of residual carrier aids demodulation (e.g., 

large doppler dynamics scenarios) and allows 

simultaneous ranging.

[2] [3] [4] 

Polarization LHCP and/or RHCP

Symbol Rate 0.5 ksps ≤ Rs ≤ 64 ksps

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index:

0.2 to 1.8 radians (Peak)

Radiometric Ranging 

Options

PN Ranging

Ranging Modulation Index: 0.2 to 

1.0 radians (Peak)

Chip rate: up to 4 Mcps 

Coding and Framing • LDPC 1⁄2 (2048, 1024)

• Uncoded, Message Size 16,384 

bits

[6] [8] [9]

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 414.1-B

[10]

Table B-30: XD4 - X-band Downlink High-Rate Data Only 

XD4 - X-band Downlink High-Rate Data Only 

Parameter Description Notes

Frequency Range 8450-8500 MHz See CCSDS 401.0-B- Section 2.4.17A for 

explanation of Filtered OQPSK and GMSK.

Allows for higher data rates with bandwidth 

efficiency.

Polarization LHCP and/or RHCP

Symbol Rate 128 ksps ≤ Rs ≤ 10 Msps

Modulation Filtered OQPSK or GMSK

Radiometric Ranging 

Options

No

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

[6] [7] [8] [9] 

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B

[10]
LNIS V005 August 31, 2023 78

Table B-31: KU1 - K-band Uplink High-Rate Data Only

KU1 - K-band Uplink High-Rate Data Only

Parameter Description Notes

Frequency Range 22.55-23.15 GHz See CCSDS 401.0-B- Section 2.4.17A for 

explanation of Filtered OQPSK and GMSK.

Allows spectrally efficient high data throughputs with 

simpler implementation than VCM.

[12] 

Polarization LHCP and/or RHCP

Symbol Rate 2 Msps ≤ Rs ≤ 50 Msps {TBR}

Modulation Filtered OQPSK or GMSK

Radiometric Ranging 

Options

Frame ranging [RD24, RD25]

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

[6][7][8][9] 

Applicable Documents CCSDS 131.0-B

CCSDS 401.0-B

[10][11] 

Table B-32: KU2 - K-band Uplink High Data w/ Ranging

KU2 - K-band Uplink High Data w/ Ranging

Parameter Description Notes

Frequency Range 22.55-23.15 GHz See CCSDS 401.0-B- Section 2.4.22A for an 

explanation of ranging implementation of 

GMSK+PN

To be recommended for K-band DWE.

Allows simultaneous ranging on K-band signals. 

[2] [12] 

Polarization LHCP and/or RHCP

Symbol Rate 2 Msps ≤ Rs ≤ 50 Msps {TBR}

Modulation GMSK+PN

Radiometric Ranging 

Options

Yes

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 (8160, 7136)

[6][7][8][9] 

Applicable 

Documents

CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 414.1-B

[10] [11] 

Table B-33: KD1- K-band Downlink High-Rate Data Only 

KD1 - K-band Downlink High-Rate Data Only

Parameter Description Notes

Frequency Range 25.5-27.0 GHz See CCSDS 401.0-B- Section 2.4.17A for 

explanation of Filtered OQPSK and GMSK.

Allows spectrally efficient high data throughputs with 

simpler implementation than VCM.

[12]

Polarization LHCP and/or RHCP

Symbol Rate 2 Msps ≤ Rs ≤ 200 Msps {TBR}

Modulation Filtered OQPSK or GMSK

Radiometric Ranging 

Options

Frame ranging [RD24, RD25]

Coding and Framing • LDPC 1⁄2 (32768, 16384)

• LDPC 4/5 (20480, 16384)

• LDPC 7/8 Rate (8160, 7136)

[6][7][8][9] 

Applicable 

Documents

CCSDS 131.0-B

CCSDS 401.0-B

[10] 
LNIS V005 August 31, 2023 79

Table B-34: KD2 - K-band Downlink High Data w/ Ranging

 

KD2 - K-band Downlink High Data w/ Ranging

Parameter Description Notes

Frequency Range 25.5-27.0 GHz See CCSDS 401.0-B- Section 2.4.22A for an 

explanation of the ranging implementation of 

GMSK+PN.

To be recommended for K-band DWE.

Allows simultaneous ranging on K-band signals. 

[2][12] 

Polarization LHCP and/or RHCP

Symbol Rate 2 Msps ≤ Rs ≤ 200 Msps {TBR}

Modulation GMSK+PN

Radiometric Ranging 

Options

Yes

Coding and Framing • LDPC 1⁄2 Rate (32768, 16384)

• LDPC 4/5 Rate (20480, 16384)

• LDPC 7/8 Rate (8160, 7136)

[6][7][8][9] 

Applicable 

Documents

CCSDS 131.0-B

CCSDS 401.0-B 

CCSDS 414.1-B

[10][11] 
LNIS V005 August 31, 2023 80

B.III LNSP-USER CONTINGENCY INTERFACES

Contingency mode signals are those used during off nominal or emergency states, when power is limited,

or antenna pointing is compromised. 

The following general notes apply to the contingency mode signals:

A. Fixed symbol rates are used for contingency mode signals to further promote interoperability and 

standardization, whereas in standard Proximity and DWE signals modes more flexibility is given 

to user platforms. The rationale for this decision is a reduced need for flexibility of symbol rate in 

the contingency mode signals, and a greater need for interoperability and standardization to 

promote availability of contingency mode support. Some flexibility is given by providing two 

options for each contingency interface, a very low symbol rate or a slightly higher symbol rate.

B. A subcarrier signal is used for contingency mode operations in order to support carrier tracking and 

aid demodulation. These signals can be used as data only, ranging only, or data and ranging 

simultaneously. When doing data and ranging simultaneously (especially in contingency mode 

operations), careful consideration must be made regarding the modulation depth of the ranging and 

data signals and the interaction between them. The footnotes provide further guidance.

C. Low-Density Parity Check (LDPC) codes are shown here in parenthetical (n, k) format, where n is 

the codeword length in bits and k is the information block length in bits. The code rate is also 

shown, although this can also be derived by rr = kk/nn. CCSDS 231.0-b Section 4 describes the 

LDPC 1⁄2 (128, 64) and LDPC 1/2 (512, 256) codes, which are used for the contingency mode 

signals described below.

D. In addition to the modes shown below, LNSPs should be capable of disabling FEC on any of the 

nominal mode’s signals specified in User Proximity interfaces and DWE interfaces as a 

contingency mode option.

The following notes apply to particular User Contingency signal formats, with the notes referred to in the 

signal specifications in the following subsections.

[1] The modulation index ranges provided here are a recommendation to ensure minimum 

interoperability of LNSPs. Users may request modulation index ranges outside this range, assuming 

they can get appropriate approvals and find an LNSP with the capability to service them.

[2] The use of simultaneous ranging with data requires consideration on the interaction between the 

carrier, data signal, and ranging signal. The ECSS Radio Frequency and Modulation handbook, 

ECSS-E-ST-50-05C Rev 2 Section 6.1.6 provides a useful rule-of-thumb: the combined peak 

modulation index (sum of data and ranging modulation indices) should not exceed 1.75 radians. 

This interoperability specification does not prohibit violation of this rule, but it is strongly 

recommended to consider the performance of simultaneous ranging and data transmission in such 

circumstances.

[3] See CCSDS 231.0-B for description of LDPC short codes 1/2 (128, 64) and 1⁄2 (512, 256).

[4] LDPC codes can be used with transfer frames up to the CCSDS limit (currently 524,288 bits for 

USLP, 16,384 bits for AOS) using slicing. See CCSDS 131.0-B Chapter 8 and Chapter 11.

[5] All transfer frames shall be either AOS or USLP

[6] The most recent version of the applicable standard shall be used, unless stated otherwise.

[7] Applicable documents for some signals are to be determined. Standards development and 

coordination for lunar proximity communications is an ongoing effort. Future coordination with 

CCSDS to clarify these applications is planned. In some cases, the CCSDS standard specifically 

refer to usage for telemetry or telecommand but not both. The LunaNet specifications are 
LNIS V005 August 31, 2023 81

symmetric in the return and forward directions, and therefore sometimes apply telemetry standards 

to telecommand links and vice-versa. This discrepancy between CCSDS recommendations and 

LunaNet specifications is realized and future clarification in coordination with CCSDS will be 

provided. 
LNIS V005 August 31, 2023 82

Table B-35: PFC1a - Proximity Forward S-band Contingency

PFC1a - Proximity Forward S-band Contingency

Parameter Description Notes

Frequency Range 2025-2110 MHz See CCSDS 401.0-B Section 2.2.4 for 

explanation of PCM/PSK/PM.

Lowest rate used for very weak signal 

links.

[1][2]

Polarization LHCP and/or RHCP

Symbol Rate 15.625 sps

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index: 0.2 to 1.8 

radians (Peak) 

Subcarrier Freq. (Sine): 16 kHz

Radiometric Ranging 

Options

PN Ranging on carrier

Ranging Modulation Index: 0.2 to 1.4 

radians (peak) 

Chip rate: up to 2.3 Mcps

Coding and Framing • LDPC 1⁄2 (128, 64) [3][4][5]

Applicable Documents CCSDS 401.0-B

CCSDS 231.0-B

[6][7]

Table B-36: PFC1b - Proximity Forward S-band Contingency

PFC1b - Proximity Forward S-band Contingency

Parameter Description Notes

Frequency Range 2025-2110 MHz See CCSDS 401.0-B Section 2.2.4 for 

explanation of PCM/PSK/PM.

Higher rate to provide flexibility for 

cislunar space operations. 

[1][2] 

Polarization LHCP and/or RHCP

Symbol Rate 250 sps

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index: 0.2 to 1.8 

radians (Peak) 

Subcarrier Freq. (Sine): 16 kHz

Radiometric Ranging 

Options

PN Ranging on carrier

Ranging Modulation Index: 0.2 to 1.4 

radians (peak) 

Chip rate: up to 2.3 Mcps

Coding and Framing • LDPC 1⁄2 Rate (512, 256) [3][4][5]

Applicable Documents CCSDS 401.0-B

CCSDS 231.0-B

[6][7]
LNIS V005 August 31, 2023 83

Table B-37: PRC1a - Proximity Return S-band Contingency 

PRC1a - Proximity Return S-band Contingency 

Parameter Description Notes

Frequency Range 2200-2290 MHz See CCSDS 401.0-B Sections 2.2.4, 2.4.3, 

and 2.4.7 for explanation of PCM/PSK/PM.

Lowest rate used for very weak signal links.

[1][2]

Polarization LHCP and/or RHCP

Symbol Rate 15.625 sps

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index: 0.2 to 1.8 

radians (Peak)

Subcarrier Freq. (Sine): 16 kHz

Radiometric Ranging 

Options

PN Ranging on carrier

Ranging Modulation Index: 0.2 to 1.0 

radians (peak)

Chip rate: up to 2.3 Mcps

Coding and Framing • LDPC 1⁄2 (128, 64) [3][4][5]

Applicable Documents CCSDS 401.0-B

CCSDS 231.0-B

[6][7]

Table B-38: PRC1b - Proximity Return S-band Contingency 

PRC1b - Proximity Return S-band Contingency

Parameter Description Notes

Frequency Range 2200-2290 MHz See CCSDS 401.0-B Sections 2.2.4, 2.4.3, 

and 2.4.7 for explanation of PCM/PSK/PM.

Higher rate to provide flexibility for 

cislunar space operations.

[1][2]

Polarization LHCP and/or RHCP

Symbol Rate 250 sps

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index: 0.2 to 1.8 

radians (Peak)

Subcarrier Freq. (Sine): 16 kHz

Radiometric Ranging 

Options

PN Ranging on carrier

Ranging Modulation Index: 0.2 to 1.0 

radians (peak)

Chip rate: up to 2.3 Mcps

Coding and Framing • LDPC 1⁄2 (512, 256) [3][4][5] 

Applicable Documents CCSDS 401.0-B

CCSDS 231.0-B [6][7] 
LNIS V005 August 31, 2023 84

Table B-39: CU1 - X-band Uplink Contingency

CU1 - X-band Uplink Contingency

Parameter Description Notes

Frequency Range 7190-7235 MHz See CCSDS 401.0-B Section 2.2.4 for 

explanation of PCM/PSK/PM.

Lowest rate typically used for deep space.

[1][2] 

Polarization LHCP and/or RHCP

Symbol Rate 15.625 sps

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index: 0.2 to 1.8 

radians (Peak) 

Subcarrier Freq. (Sine): 16 kHz

Radiometric Ranging 

Options

PN Ranging

Ranging Modulation Index: 0.2 to 1.4 

radians (Peak)

Chip rate: up to 4 Mcps

Coding and Framing • LDPC 1⁄2 (128, 64) [3][4][5]

Applicable Documents CCSDS 401.0-B

CCSDS 231.0-B

[6]

Table B-40: CU2 - X-band Uplink Contingency

CU2 - X-band Uplink Contingency

Parameter Description Notes

Frequency Range 7190-7235 MHz See CCSDS 401.0-B Section 2.2.4 for 

explanation of PCM/PSK/PM.

Higher rate to provide flexibility for 

cislunar space operations.

[1][2] 

Polarization LHCP and/or RHCP

Symbol Rate 250 sps

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index: 0.2 to 1.8radians 

(Peak)

Subcarrier Freq. (Sine): 16 kHz

Radiometric Ranging 

Options

PN Ranging on carrier

Ranging Modulation Index: 0.2 to 1.4 

radians (peak)

Chip rate: up to 4 Mcps

Coding and Framing • LDPC 1⁄2 (512, 256) [3][4][5] 

Applicable Documents CCSDS 401.0-B

CCSDS 231.0-B

[6] 
LNIS V005 August 31, 2023 85

Table B-41: CD1 - X-band Downlink Contingency

CD1 - X-band Downlink Contingency

Parameter Description Notes

Frequency Range 8450-8500 MHz See CCSDS 401.0-B Sections 2.2.4, 2.4.3, 

and 2.4.7 for explanation of PCM/PSK/PM. 

Lowest rate typically used for deep space.

[1][2] 

Polarization LHCP and/or RHCP

Symbol Rate 20 sps

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index: 0.2 to 1.8 

radians (Peak)

Subcarrier Freq. (Sine): 16 kHz

Radiometric Ranging 

Options

PN Ranging

Ranging Modulation Index: 0.2 to 1.0 

radians (Peak)

Chip rate: up to 4 Mcps

Coding and Framing • LDPC 1⁄2 (128, 64) [3][4][5] 

Applicable Documents CCSDS 401.0-B

CCSDS 231.0-B

[6] [7] 

Table B-42: CD2 - X-band Downlink Contingency

CD2 - X-band Downlink Contingency

Parameter Description Notes

Frequency Range 8450-8500 MHz See CCSDS 401.0-B Sections 2.2.4, 2.4.3, 

and 2.4.7 for explanation of PCM/PSK/PM. 

Higher rate to provide flexibility for cislunar 

space operations. 

[1][2] 

Polarization LHCP and/or RHCP

Symbol Rate 250 sps

Modulation PCM/PSK/PM+NRZ-L

Data Modulation Index: 0.2 to 1.8 

radians (Peak)

Subcarrier Freq. (Sine): 16 kHz

Radiometric Ranging 

Options

PN Ranging

Ranging Modulation Index: 0.2 to 1.0 

radians (Peak)

Chip rate: up to 4 Mcps

Coding and Framing • LDPC 1⁄2 (512, 256) [3][4][5] 

Applicable Documents CCSDS 401.0-B

CCSDS 231.0-B

[6] [7] 

 
LNIS V005 August 31, 2023 86

APPENDIX C NAVIGATION PARAMETERS

The AFS service is enabled using a spread spectrum signal structure similar to the ones used in GNSS, 

allowing significant reuse of GNSS spaceborne receivers. The signal will be broadcast in the 2483.5-2500 

MHz frequency range, being the band designed for radionavigation in recommendation SFCG 32-2R5 from 

the SFCG CDMA allows different LNSP sources to provide the AFS service simultaneously at a single and 

common S-band frequency, and individual, orthogonal PN codes will be assigned to each LNSP node 

implementing this service. [AD1] will identify the method to assign PN codes to LNSP nodes.

Modulations adopted will be in line with current GNSS signals, by utilizing Bi-Phase Shift Keying (BPSK)

modulations. Two channels are identified, one in-phase (I) and one in quadrature phase (Q). The I-channel

is intended to facilitate acquisition and navigation capabilities and serve as a data channel. The I-channel 

will consist of a BPSK (1) modulation, utilizing a spreading code at 1.023 Mcps. This data channel is used 

to disseminate LunaNet messages, carrying navigation, general access, alerts, and SAR information. The 

Q-channel is intended to provide higher accuracy PNT services, in the form of a pilot channel, carrying no 

data and employing different PN codes to maximize cross-correlation properties. Q-channel will employ 

BPSK (5) modulation with a spreading code at 5.115Mcps. Chip-rates for both channels will be 

synchronized with each other and coherently related to a mutual carrier frequency reference.

To transmit a carrier center frequency of 2492.028 MHz, the reference clock can be at 1.023MHz utilizing 

a reference clock multiplier of 2436. The detailed definition of the signal is provided in the LunaNet SignalIn-Space Recommended Standard - Augmented Forward Signal [AD1] document. Note that the signal 

structure and the LANS service in section 3.2.2 will be used for all LunaNet nodes broadcasting the 

AFS/PFS5 signal. 

Messages that will be transmitted as part of AFS on PFS5 are identified in Appendix D and as detailed in 

[AD1].

Each LNSP shall ensure the AFS maintains Signal-In-Space-Errors (SISE) within the requirement specified 

in Table C-1 within the defined service volume. 

The SISE is defined as the instantaneous difference between the position, velocity, and time of a LunaNet 

node as broadcasted by that node’s navigation message and the true satellite PVT respectively expressed in 

the lunar reference system and the lunar time system standard [AD5].

This definition is independent of the orbital characteristics of each LunaNet node and establishes an upper 

bound on the error experienced at user level that is the result of the projection of the SISE onto the usersatellite direction [RD 25]. This allows users to derive reliable navigation solutions at a dependable level 

when using LANS from different LNSPs. The SISE consists of a combination of errors that are the 

responsibility of the LNSPs, such as:

[1] LNSP ephemeris uncertainties or errors in the orbital products tendered to users, as represented in 

the lunar reference frame.

[2] LNSP timing errors due to time knowledge uncertainties, inaccurate clock correction information 

conveyed to users, or misalignments of time with the signal realization.

[3] Uncalibrated or unknown LNSP group delays due to code phase offsets, antenna phase offsets and 

variations, unaccounted transmit path delays and variations, code-to-code incoherency, code-tocarrier incoherency, etc.
LNIS V005 August 31, 2023 87

The SISE can be expressed for convenience in two parts: 

1. Signal-In-Space Error for positioning (SISE pos) 

Where xx, yy, zz,tt are the true position and time, while the corresponding tilde parameters represent the 

values broadcasted in the navigation message. 

2. Signal-In-Space Error for velocity (SISE vel): 

 Where xẋ, yẏ, zżrepresents the velocity and ctṫ the clock drift. 

Table C-1: LNSP SISE

Error Value

SISE pos

≤TBD m (95%) - Calculated as the 95th 

percentile of the time series of instantaneous 

SISE values over a TBD hours period.

SISE vel

≤TBD m/s (95%) - Calculated as the 95th 

percentile of the time series of instantaneous

SISE values over a TBD hours period.

Table C-2: Proximity Link Supporting Signals

[1] "TBW" indicates this item is to be worked.

[2] "O" indicates the signal supports the ability to provide the service.

[3] "X" indicates it is mandatory for the signal to provide the service.

SSSSSSSSpppppp = �(xx − xx�)2 + (yy − yy�)2 + (zz − zz̃)2 + (ctt − ctt̃)2 , 1 

SSSSSSSSvvvvvv = �(xẋ − xẋ �)2 + (yẏ − yẏ �)2 + (zż − zż ̃)2 + (ctṫ− ctṫ ̃)2 , 2 
LNIS V005 August 31, 2023 88

Table C-3: Proximity Link Supporting Signals

[1] "TBW" indicates this item is to be worked.

[2] "O" indicates the signal supports the ability to provide the service.

[3] "X" indicates it is mandatory for the signal to provide the service.

[4] “1” To provide the 2-way Doppler Measurement, PRS5 must be coherent with a PRFx signal which 

may be other than PRF5.
LNIS V005 August 31, 2023 89

APPENDIX D LUNANET MESSAGES

D.I OVERVIEW OF MESSAGES

Messaging services provide a standard method for information to be transferred directly over a link layer 

service, a network layer service, or via dedicated message streams (e.g., AFS messages). These messaging 

services are utilized by protocols for PNT services, network acquisition, space weather alerts, search and 

rescue, and other LunaNet services. Standard messages are envisioned to be used across user proximity 

links, provider crosslinks, as well as DWE links. 

At this time, the application of messages to the P2P links and crosslinks have not been fully defined. Thus, 

it is relevant to note that the particulars of the messages on these link types may differ slightly from those 

on the AFS.

LunaNet Detailed Message Definition Document (LNIS-TBD-AD0003) [AD3] will specify all message 

formats, content, parameters, and association with each service and/or signal. An overview is provided 

herein, starting with that lists the message ID, message title, and a brief description. 

Table D-1: Message Identification

MSG ID MSG Title Description

MSG-G1 LunaNet Network 

Access Information

Identifies attributes needed to access network services. Informs users 

of basics applicable to LNSP nodes, such as services offered and 

bands, update rate of messages. May include other messages plus 

additional info, such as almanac, MLN Antenna Properties, H&S.

MSG-G2 Health and Safety

Health status of the service(s) provided by the LNSP node and is 

specific to the LNSP node. Health status of other LNSP nodes is 

provided as part of MSG-G5 MOrbit Almanac.

MSG-G3 MAntennaProperties

Information about the transmission antenna properties (e.g.: antenna 

offset from CG in body frame, articulating or static, proximity signal 

FOVs, attitude (3-axis, nadir, or other)). Default information can be 

specified in the standard. LNSP must identify default values of the 

antenna properties in their ICDs. If an LNSP is fully compliant with 

the default values in the ICDs this message might be omitted. On the 

contrary, if the LNSP is not compliant with the default specification, 

they shall disseminate this message. At the user level, this is 

transparent: the user will receive the messages and interpret them as 

needed.

MSG-G4 Sorbit Ephemeris & 

clock correction

Precise ephemeris, path delays, and clock corrections of the satellite 

that is transmitting the signal. This message will also contain (if 

required) the clock offset between the LNSP time to the lunar 

reference time. This is specific for PNT, not to be confused with 

MSG-G5 MOrbitAlmanac. The message will broadcast the parameters 

to be used in the orbital model defined in the LNSP-specific 

documentation (e.g., ICD).

Table D-2 provides the following information for each message transmitted via AFS. 
LNIS V005 August 31, 2023 90

MSG ID MSG Title Description

MSG-G5 MOrbit Almanac

Parameters of the orbital model (low accuracy model, ~km orbit 

position accuracy, ~m/s orbit velocity accuracy) of all the satellites in 

the LNSP constellation.

This message will also (optionally, TBD) include the health status of 

the services provided by all the LNSP nodes.

MSG-G6 SOrbit Almanac

Parameters of the orbital model (low accuracy model on the order of 

km orbital position accuracy and m/s orbital velocity accuracy) of the 

LNSP node transmitting the signal.

MSG-G7 SOrbitState / Location Location Service information to user, whether on surface or in orbit.

MSG-G8 Time of transmission Time information provided at the defined edge of a synchronization 

symbol within the navigation message.

MSG-G9

Time and Frequency 

Synchronization 

(frame)

Time information provided to allow implementation of navigation 

services other than LANS or a dedicated CDMA signal.

MSG-G10 Maneuver Announces a planned maneuver of an LNSP satellite to the users and 

network, or of a user to an LNSP for Location Service.

MSG-G11 SAttitude State/

Ephemeris

Attitude information of the satellite. This message could implement 

the parameters of an attitude model to allow the user to compute the 

current and future attitude of the transmitting satellite. Alternatively, a 

time series of already computed attitude information could be 

broadcast to the user. 

MSG-G12 MAttitudeEphem Attitude information of multiple satellites, e.g., the constellation of 

LNSP nodes.

MSG-G13 Observations Information on metric tracking measurements (observations) 

performed by one entity that is forwarded to a separate entity.

MSG-G14 Conjunction 

Announces a potential conjunction between lunar orbiters. This 

concept could be like the CCSDS standard for Conjunction Data 

Message exchanges.

MSG-G15 Maplet

Map information for specific selenographic sectors or seleno-global. 

Details to be worked on specific content; concepts include sector index 

ID, current versions, delta update information from reference to limit 

dissemination time.

MSG-G16 Map Comprehensive Full high resolution digital elevation map for specific lunar surface 

selenographic sector(s).

MSG-G17 Ancillary info Basic data required for PNT, for example reference frames, coordinate 

transformations, lunar potential models, lunar ephemeris, lunar 

orientation parameters, covariance, and state transition matrix.

MSG-S18 Search and Rescue 

Alert

Alert from Search and Rescue beacon.
LNIS V005 August 31, 2023 91

MSG ID MSG Title Description

MSG-G5 MOrbit Almanac

Parameters of the orbital model (low accuracy model, ~km orbit 

position accuracy, ~m/s orbit velocity accuracy) of all the satellites in 

the LNSP constellation.

This message will also (optionally, TBD) include the health status of 

the services provided by all the LNSP nodes.

MSG-G6 SOrbit Almanac

Parameters of the orbital model (low accuracy model on the order of 

km orbital position accuracy and m/s orbital velocity accuracy) of the 

LNSP node transmitting the signal.

MSG-G7 SOrbitState / Location Location Service information to user, whether on surface or in orbit.

MSG-G8 Time of transmission Time information provided at the defined edge of a synchronization 

symbol within the navigation message.

MSG-G9

Time and Frequency 

Synchronization 

(frame)

Time information provided to allow implementation of navigation 

services other than LANS or a dedicated CDMA signal.

MSG-S19 Acknowledge- of SAR 

- LvL1

Automatic acknowledge at the LNSP satellite level of receipt of a SAR 

beacon distress message. This does not mean the message has been 

processed by the SAR ground system.

MSG-S20 Acknowledge- of SAR 

- LvL2

Acknowledgement that the SAR beacon alert request has been 

correctly received at the control center and that a rescue operation has 

started (also called LunaSAR return message).

MSG-G21 User Message Request Request by user for specific message.

MSG-G22 Acknowledge- of nonSAR MSG

Automatic acknowledge at the LNSP satellite level of receipt of a user 

request (non-SAR). Note that this is not the response to the request, 

but simply an acknowledgement of receipt.

MSG-G23 GNSS Augmentation 

Augmentation information (e.g., satellites ephemeris) on Earth GNSS 

satellites to support the use of Earth GNSS signals by GNSS sensitive 

receivers in cislunar space.

MSG-G24 Detection Alert Used to broadcast an alert that must be disseminated to the users.

MSG-G25 Science Disseminates science-specific data.

MSG-G26 UIS Request Request from user for services from an LNSP.

MSG-G27 UIS Response Notification to user indicating response to the UIS Request.

MSG-G28 User Schedule Notice Notification to user of upcoming service schedule that needs to be 

disseminated to ensure receipt prior to an upcoming P2P contact.

MSG-G29 FF Commands Specific user commands or information needed rapidly by user, 

distributed via broadcast.

Under each PNT sub-service, a label is used to identify which category applies to that message/service 

combination within the available AFS bandwidth: F = Fundamental, meaning it shall be broadcasted by the 
LNIS V005 August 31, 2023 92

LNSP; O = Optional, meaning it might be broadcasted by the LNSP; and C = Comm, meaning it can be 

transmitted on AFS to facilitate LunaNet services. In Table D-2 below, fields that are grey with a dash 

indicate the fact that the message is not provided over the service link.

• Periodicity: “Periodic” means the message is transmitted at a regular cadence; “ad-hoc” means the 

message is sent only when needed or requested.

• Cadence: Identifies the time between consecutive transmission of periodic messages with the same 

message ID (e.g., MSG-Gx). Note: the message information may not be updated at this cadence, 

the actual data may be static on successive transmissions.

• Latency: Identifies the time between message generation/reception and message transmission. If 

marked N/A, there is no stringent requirement from an interoperability standpoint.
LNIS V005 August 31, 2023 93

Table D-2: LANS / AFS Messages