Jim Schier, Chief Architect & Dep. Director System Engineering

Space Communications and Navigation (SCaN) Program

September 14, 2016

Strategy and Architecture for Evolution of 

Space Comm and Navigation Networks 
Vision

• “Shrink” the solar system by connecting the principle investigator more 

closely to the instrument, the mission controller to the spacecraft, and 

the astronaut to the audience

• Improve the mission’s experience and reduce mission burden – the 

effort and cost required to design and operate spacecraft to receive 

services from the SCaN Network

• Reduce network burden – the effort and cost required to design, 

operate, and sustain the SCaN Network as it provides services to 

missions with the collateral benefit of increasing funding for C&N 

technology

• Apply new and enhanced capabilities of terrestrial telecommunications 

and navigation to space leveraging other organizations’ investments

• Enable growth of the domestic commercial space market to provide –

and NASA to use – commercial services currently dominated by 

government capabilities

• Enable greater international collaboration and lower costs in space by 

establishing an open architecture with interoperable services that foster 

commercial competition and can be adopted by international agencies 

and as well as NASA 2
Shift: RF to RF + Optical

• Transition Laser Comm Relay Demo (LCRD) to 

operations after 2019-2021 demonstration phase 

for initial Earth Network optical capability by 

~2021

• LEO terminal being developed for ISS as 1st user

• Discovery AO incentivized bidders for deep space 

optical

– 3 of 5 bids selected chose to include an optical payload

• Optical technology promises

– High data rates with low SWaP & cost for users & relays 

– Optical platform’s built-in vibration isolation reduces 

impact on spacecraft bus of gimbaled antenna

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Shift: Single Access to Multiple Access

• Under-utilizing network: Missions use TDRSS 

Single Access at a fraction of capacity

– HST uses S-band SA at 1 Mbps – TDRS max rate is 

300 Mbps

• Approach: Match structure of network services 

to mission usage characteristics by expanding 

use of Multiple Access & reducing use of Single 

Access

– Introduce demand access service: user requests 

access when he needs it & gets BW that he needs

4
Single Access vs. Multiple Access

• Single Access points one network antenna to one user antenna 

& commits both for duration of event  connection-oriented 

like telephone switchboards

• Multiple Access enables one network antenna to talk to 

multiple users simultaneously in same overall system bandwidth

5

NEN

DSN Dedicated SpaceGround Link to Ground 

Terminal

User-TDRS SA Link for Event SN

User-Network 

Link for Event

NEN

DSN

DSN: 

• Multiple S/C Per Antenna (MSPA)

• Opportunistic MSPA

NEN: TBD

Dedicated SpaceGround Link to Ground 

Terminal

User-TDRS MA 

Links for Events SN
Shift: Scheduled to Unscheduled Access 

• All missions schedule events (passes) days-weeks in 

advance 

– Process is labor-intensive

• Unreliable data delivery forces missions to schedule 

extra events & repeat transmissions

– Scheduling is NP-hard – TDRSS schedules ~60% efficient

• Approach:

– Expand use of Multiple Access; reduce Single Access

– Introduce demand access services 

– Shift from (unreliable) link layer to (guaranteed) network 

layer service using Disruption Tolerant Networking (DTN)

• Result: Eliminate scheduling for most missions

– Enables further system automation & operations cost 

reduction

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Shift: Switch from Ku- to Ka-band

• Spectrum pressure: NASA agreed to NTIA direction 

to move out of Ku-band space-to-space 

(eventually)

– NASA incorporated Ka-band starting with TDRS H (2000)

– NASA also obtained Ka-band space-to-ground allocation

• Ka-band can provide higher data rates at higher 

frequencies with lower spacecraft SWaP 

– Need to invest in user terminals to bring cost down & 

overcome user community reluctance to adopt Ka

• Eliminate Ku-band from Next Gen Earth Relay

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Services: Link Layer to Network Layer

• Link layer services don’t guarantee data delivery 

– Mission Operations Centers (MOC) develop SW to 

process data for errors, resend data, command s/c 

when to delete data from memory

– Application layer protocols such as CCSDS File Delivery 

Protocol (CFDP) with Automatic Repeat Request (ARQ) 

provide reliable delivery over unreliable link layer 

protocols such as Space Packet

• Expand services to include space internetworking 

(Solar System Internet, SSI, using IP & DTN)

– DTN guarantees delivery obviating need for MOC 

processing & retransmission reducing burden on both 

user ground & flight segments

• SSI enables a Service-Oriented Architecture (SOA) that 

can provide many added apps

• Data can move directly from MOC/MCC to PI or 

directly from spacecraft to PI

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Current SCaN Network Service 

Future SCaN SSI Service 
Planetary Networks: 

Earth, Moon and Mars – One Architecture 

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Architect for Flexibility, Scalability, and Affordability –

Implement as required to meet specific mission needs

Deep 

Space 

Habitat

GEO HMO

LEO LMO

Proximity 

Links

SCGS

Trunk 

link

Proximity 

Links

Earth Relay Mars Relay

Scienc

e 

Orbiter

Science/ 

Relay 

Orbiter

Lander

Phobos 

Exploratio

n Vehicle

Earth Network Mars Network 

HLO

LLO

Proximity 

Links

Lunar Relay

Science/ 

Relay 

Orbiter Science 

Orbiter

Lander

Lunar Network

Exploration 

Habitat

Distant 

Retrograde 

Orbit (DRO)

DTE/ 

DFE

Benefits of Planetary Networks:

• Reduced mission burden with short links for in-system communications - enables insystem telerobotics

• Common architecture reduces technology and development costs

• Reuse of HW and SW: Family of products includes variants for different environments

• Reuse of spectrum
A New Mars Network for 

Human Exploration and Science

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New/enhanced Services

• Network layer service using DTN

• Timing service

• Celeslocation service: positioning 

service upgraded to provide GPSlike surface location

• Inter-agency service 

management based on the 

CCSDS CSSM standard

• Optimetric data & tracking 

services

• SOA services: Application layer 

services such as look-up, 

directory, caching, storage, 

messaging, alarms/alerts

Mars Network architecture 

• Network with dedicated relay orbiters in high Mars orbit and/or relay payloads on science orbiters

– Coverage focused on Mars Base

– Coverage includes Phobos and Deimos

• Continuous trunk line availability to Earth for low end-to-end forward/return data latency

• Deep Space Optical Capability (DSOC) terminals deployed on mission spacecraft, the dedicated 

relay orbiter, and surface elements

• Relay orbiters support return trunk line at ~150 mega-bits per second (Mbps) (Ka-band) and ~300 

Mbps (optical) as well as 50 Mbps for the forward trunk line
Tying Next Gen Architecture to SBIR

SBIR Topics Mapping to Vision Mapping to Next Gen Paradigm Shifts

Long Range 

Optical 

Communications

• “Shrink” the solar 

system

• Improve mission’s 

experience & 

reduce mission 

burden

• Reduce network 

burden

• Apply new & 

enhanced 

capabilities

• Enable growth of 

domestic comercial space market

• Enable greater 

international 

collaboration 

• RF to RF + Optical

• Single access to multiple access

• Different near Earth & deep space architectures 

to common architecture (planetary networks)

Intelligent 

Communications 

Systems

• Single access to multiple access

• Link layer to network layer service provider

Advanced RF 

Communications

• Single access to multiple access

• Switch from Ku-band to Ka-band 

• Different near Earth & deep space architectures 

to common architecture (planetary networks)

Flight Dynamics 

and Nav Tech

• RF to RF + Optical

• Scheduled to unscheduled access

Transformational 

Communications 

Technology

• Single access to multiple access

• Different near Earth & deep space architectures 

to common architecture (planetary networks)

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