**TRW Inc**. One Space Park

**Space & Electronics Group** Redondo Beach CA 90278

EOS AQUA

X-BAND DIRECT BROADCAST

INTERFACE DESCRIPTION DOCUMENT

Date: 8 June 2001 No. D26699

Rev: **A**

  --------------------------------- -------------------------------------
  Superseding:                      New

  --------------------------------- -------------------------------------

PREPARED FOR: **NASA GSFC**

**Greenbelt, MD 20771**

**CDRL 2208**

![](media/image1.png)

Copyright © 1998 TRW Inc., All Rights Reserved. This copyrighted
material was generated using funding provided by the United States
National Aeronautic and Space Administration under Contract No.
NAS5-32954.

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  **TRW Space, Defense\           One Space               TRW   
  & Information Systems**         Park\                         
                                  Redondo                       
                                  Beach, CA                     
                                  90278                         
  ------------------------------- ------------ ---------- ----- ------------
                                                                

  **Revision/Change Record**                   **For            D26699 A
                                               Document         
                                               No.**            
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  **SYMBOL**   **DATE**   **AUTHORIZATION**                                  **REVISION           **PAGES
                                                                             DESCRIPTION**        AFFECTED**

  New          4/28/98    Original PDMO                                      Initial Issue        All

                          Release                                            CDRL 2208            

                                                                                                  

                                                                                                  

  A            6/8/01                                                        Revision A Update    See Change
                                                                                                  Bars

                          \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_                        

                          G. M. Haney                                                             

                          Comm. Subsystem Mgr.                                                    

                                                                                                  

                                                                                                  

                          \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_                        

                          S. Staich                                                               

                          System Engineering Mgr.                                                 

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

                                                                                                  

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**Table of Contents**

1\. INTRODUCTION [2](#introduction)

1.1 PURPOSE [2](#purpose)

1.2 INTERFACE RESPONSIBILITIES [2](#interface-responsibilities)

1.3 INTERFACE IDENTIFICATION [2](#interface-identification)

1.3.1 RF Link Definition [2](#rf-link-definition)

1.3.2 Functional Description [3](#functional-description)

1.3.3 Link Calculations [3](#link-calculations)

1.3.4 Data Formats [3](#data-formats)

2\. DOCUMENTS [4](#documents)

2.1 Applicable Documents [4](#applicable-documents)

2.2 Reference Documents [4](#reference-documents)

2.3 Other Related Documents [4](#other-related-documents)

3\. COMMUNICATIONS FUNCTIONAL INTERFACE
[5](#communications-functional-interface)

3.1 General [5](#general)

3.1.1 Interface RF Links [5](#interface-rf-links)

3.1.2 Interface Functional Applicability
[5](#interface-functional-applicability)

3.2 Spacecraft Communications Subsystem Overview
[5](#spacecraft-communications-subsystem-overview)

3.3 Communications Performance Characteristics 7

3.3.1 Science Data Channel BER 7

3.3.2 PRBS Test Channel BER 7

3.4 Communications Functional Characteristics
[7](#communications-functional-characteristics)

3.4.1 Science Data Mode [7](#science-data-mode)

3.4.2 Pseudo-Random Bit Stream (PRBS) Mode
[7](#pseudo-random-bit-stream-prbs-mode)

4\. LINK INTERFACE CHARACTERISTICS [8](#link-interface-characteristics)

4.1 Link Functional Design [8](#link-functional-design)

4.1.1 Spacecraft to Ground Station Design
[8](#spacecraft-to-ground-station-design)

4.1.2 Spacecraft to Ground Station Functional Description
[9](#spacecraft-to-ground-station-functional-description)

4.2 Signal Characteristics and Constraints
[11](#signal-characteristics-and-constraints)

4.2.1 Science Frame Format [11](#science-frame-format)

4.2.1.1 Reed-Solomon Coding [11](#reed-solomon-coding)

4.2.1.2 Bit Transition Generator [11](#bit-transition-generator)

4.2.2 Signal Characteristics [12](#signal-characteristics)

4.2.2.1 Data Signal Format [13](#data-signal-format)

4.2.2.2 Data Rate Accuracy [13](#data-rate-accuracy)

4.2.3 Modulated Signal Constraints [13](#__RefHeading___Toc450548990)

4.2.3.1 Downlink Frequency [14](#downlink-frequency)

4.2.3.2 Downlink Frequency Stability [14](#downlink-frequency-stability)

4.2.3.3 Phase Noise [14](#phase-noise)

4.3 Downlink Acquisition and Tracking
[15](#downlink-acquisition-and-tracking)

4.3.1 EBS Station Characteristics [15](#edbs-station-characteristics)

**List of Figures**

Figure 1.3-1: RF X-band Direct Broadcast Downlink
[3](#__RefHeading___Toc450549025)

Figure 3.2-1: Communications Subsystem X-band section block diagram 6

Figure 4.1-1: Spacecraft-to-EDBS ground station downlink configuration
[9](#__RefHeading___Toc450549027)

Figure 4.2-1: Channel Access Data Unit (Sync + coded VCDU)
[11](#__RefHeading___Toc450549028)

Figure 4.2-2: Digital data Signal Formats
[13](#__RefHeading___Toc450549029)

**List of Tables**

Table 3.4-1: X-band Broadcast downlink modes
[8](#__RefHeading___Toc450549054)

Table 4.2-1: X-band Downlink Signal Characteristics
[12](#__RefHeading___Toc450549055)

Table 4.2-2: X-band Downlink Signal Constraints 14

Table 4.3-1: X-band EOS Direct Broadcast Station G/T values
[15](#__RefHeading___Toc450549057)

List of Appendices

Appendix A: Link Calculations 16

Appendix B: X-band EC Antenna Pattern 20

**Interface Description Document**

**for**

**EOS AQUA X-band Direct Broadcast**

**PREFACE**

This EOS AQUA Spacecraft Radio Frequency (RF) Interface Description
Document (IDD) describes the X-band Direct Broadcast link between EOS
AQUA Spacecraft and the Earth Observing System Direct Broadcast Stations
(EDBS).

A Document Change Notice (DCN) will be issued to update the document for
any future approved changes. Changes to this document will be controlled
through the TRW Change Control Board (CCB).

Any changes or questions concerning this document should be addressed
to:

Communications Subsystem Manager for EOS

> TRW, S&LPD

One Space Park

Redondo Beach, CA 90278

# INTRODUCTION

## PURPOSE

The Interface Description Document (IDD) describes technical aspects of
the Direct Broadcast (DB) radio frequency interface between the EOS AQUA
spacecraft and the worldwide Earth Observing System Direct Broadcast
Stations (EDBS) within line-of-sight view. The EDBS will be used to
provide DB science and engineering data service in real time via X-band
downlink transmission.

## INTERFACE RESPONSIBILITIES

Interface responsibilities are defined in terms of the Goddard Space
Flight Center (GSFC) EOS AQUA Project Office. The portion identified as
the EOS AQUA spacecraft is the responsibility of the GSFC EOS AQUA
Project Office. The design characteristics and parameters in this IDD
are subject to the joint control of the GSFC EOS AQUA Project Office and
the TRW EOS AQUA Program Office. The GSFC Operations Manager of the EOS
AQUA Project and his Designee and the Designee of the TRW EOS AQUA
Program Office will jointly approve this IDD upon resolution of issues
and discrepancies as agreed upon by these parties.

## INTERFACE IDENTIFICATION

### RF Link Definition

The communications subsystem interface defined by this IDD is the X-band
DB transmission link between the EOS AQUA spacecraft and the Earth
Observing System direct broadcast ground stations. Figure 1.3-1 depicts
the RF downlink between the Spacecraft and an EOS Direct Broadcast
Ground Station.

![](media/image2.wmf)

[]{#__RefHeading___Toc450549025 .anchor}Figure 1.3-1: RF X-band Direct
Broadcast Downlink

### Functional Description

In the Broadcast mode the spacecraft continuously transmits all
real-time instrument science data, real-time spacecraft engineering
(housekeeping) data, ground-based attitude determination data, and
instrument engineering (housekeeping) data as it travels in a
sun-synchronous near circular orbit at a nominal altitude of 705 km. The
data rate is 15 Mbps at a nominal downlink frequency of 8160 MHz. In
normal operations the Broadcast mode will be used during most of the
orbit. The only time it is not used is during the approximate 8 minutes
of every 99 minute orbit when the Playback or Downlink modes are active
in playing back stored or real time data to the two Earth Observing
System Polar Ground Stations (EPGS). The RF interfaces between the EOS
AQUA Spacecraft and the EPGS are defined in a separate RF Interface
Control Document (ICD) referenced in Section 2.

### Link Calculations

The RF link calculations contained in Appendix A for the Spacecraft
modes of operation are included only as supporting data and do not
constitute a formal part of the IDD agreement. The X-band earth coverage
antenna pattern data provided in Appendix B are included for information
purposes and are also not a formal part of this IDD.

### Data Formats

The data contents and formats are described in Section 6 of D22262
(Reference Document 2.2.a).

# DOCUMENTS

## Applicable Documents

The following documents are applicable to the E0S AQUA Spacecraft. In
the event of conflict between this IDD and the documents listed below,
the documents below govern.

> a\. GSFC-422-13-11-01, EOS-Common Spacecraft Specification, August
> 1994.
>
> b\. SS6-0165, TRW EOS Common Spacecraft Communications Subsystem
> Specification, 23 June 1997

## Reference Documents

The following documents are reference documents applicable to the RF
interface. These documents do not form a part of this IDD and are not
controlled by their reference herein.

> a\. D22262, Interface Control Document between the EOS PM-1 Spacecraft
> and the EOS Ground System, October 1998.
>
> b\. EPGS document, Radio Frequency Interface Control Document between
> the EOS AQUA Spacecraft and the EOS Polar Ground Stations (EPGS) and
> the Wallops Island Station (WPS), February 1999, DCN 001.
>
> c\. GSFC 422-11-12-01, General Interface Requirement Document for EOS
> Common Spacecraft/Instruments, January 1994.
>
> d\. GSFC EOS Mission Operations Concept Document, March 1993.

## Other Related Documents

The following documents are listed for the convenience of the user.
These documents do not form a part of this IDD and are not controlled by
their reference herein.

> a\. CCSDS 701.0-B-2 \"Advanced Orbiting Systems, Networks and Data
> Links: Architectural Specification\", Issue 1, Blue Book, Consultative
> Committee for Space Data Systems, November 1992.
>
> b\. CCSDS 101.0 B-3 \"Telemetry Channel Coding\" Blue Book, May 1992.

# COMMUNICATIONS FUNCTIONAL INTERFACE 

## General

### Interface RF Links

This section defines the required RF communication downlinks:

> 1\. Spacecraft-to-EDBS X-band Direct Broadcast (DB) data link
>
> 2\. Spacecraft-to EDBS X-Band Direct Broadcast Pseudo-Random Bit
> Stream (PRBS) link

### Interface Functional Applicability

The RF communications interface functional and performance capabilities
shall be applicable to the following project phases:

> a\) RF Compatibility Testing
>
> b\) End-to End (ETE) Testing: Full X-band capability
>
> c\) Pre-launch: Check-out
>
> d\) Orbit acquisition initialization and orbit acquisition: X-band
> communication links
>
> f\) Operations Phase - Full X band communications capability
>
> g\) End-of-Mission phase: X-band communication links

## Spacecraft Communications Subsystem Overview

> A block diagram of the X-band section is shown in Figure 3.2-1. It
> consists of two modulators, a hybrid coupler, two traveling wave tube
> amplifiers (TWTAs), two isolators, a waveguide switch, a bandpass
> filter, a lowpass filter, and an X-band earth coverage antenna.
>
> Each of the identical modulators receives broadcast or playback I and
> Q channel data from the Formatter Multiplexer Unit (FMU) in the
> Command and Data Handling (C&DH) subsystem. A clock signal is output
> from the active modulator to the FMU, setting the modulator input data
> rate. For the AQUA mission, the data rate is 15.Mbps using the Direct
> Broadcast link. The I& Q channels are balanced and alternating bits of
> the data stream are placed on each channel at 7.5.Mbps. The incoming
> data is then directly Staggered Quadriphase Shift Key (SQPSK)
> modulated onto an 8160.MHz carrier. The resulting RF signal is then
> sent to the active TWTA via the 3 dB hybrid coupler. The coupler
> provides cross strapping between the redundant modulators and
> redundant TWTAs.
>
> Each X-band TWTA consists of a traveling wave tube and power
> converter. The power converter generates the required traveling wave
> tube voltages from the spacecraft DC power bus. To prevent TWTA damage
> and/or performance degradation due to potential voltage reflection an
> isolator is used at the TWTA output. The active TWTA amplifies the
> modulated input signal to a nominal saturated output power of 25.Watts
> (23.Watts EOL minimum). The resulting RF signal is routed through a
> waveguide switch to the filters. This switch provides a two-for-one
> redundancy of the RF signal path.
>
> Prior to transmission through the earth coverage antenna, the TWTA
> output signal is filtered by a bandpass filter and a lowpass filter.
> The purpose of the filters is twofold. First, the bandpass filter
> reduces the portion of the spectrum falling within the Deep Space
> Research band (8400.MHz to 8450.MHz) to meet the CCIR recommended
> power spectral density requirement at the ground. Second, the lowpass
> filter suppresses harmonic components to comply with on-board
> instrument noninterference requirements.
>
> After filtering, the signal is radiated with Right Hand Circular
> Polarization (RHCP) through the X-band earth coverage antenna. The
> antenna is mounted at the end of a boom that is developed after launch
> to obtain a full earth field-of-view. Across a 63.8 degree half cone
> angle the reflector is shaped to provide approximately constant power
> density to any earth station with line-of-sight view as the spacecraft
> passes overhead. Since a 5 degree ground station elevation angle
> corresponds to 63.8 degrees from antenna Nadir, the cone represents
> the nominal operating beamwidth of the antenna.
>
> ![](media/image3.wmf)

Figure 3.2-1: Communications Subsystem X-band Section Block Diagram

## communications performance characteristics

RF link performance characteristics for the communications functional
capability described in Paragraph 3.4 are defined in this section. The
EDBS communications performance characteristics are based on the
presumption that the Spacecraft and EDBS each perform in accordance with
the X-band performance parameters defined in Section 4.

### Science Data Channel BER

The maximum X-band downlink BER for the detected digital science data in
the data channel shall be ≤10^-3^, referenced to the input of a
Reed-Solomon Decoder on the ground. This assumes the link meets the
characteristics given in Sections 4.2 and 4.3.

### PRBS Test Channel BER

The maximum X-band downlink BER for the PRBS test channel shall be
≤10^-3^ referenced to the input of a Reed-Solomon decoder on the ground.
This assumes the link meets the characteristics given in Sections 4.2
and 4.3.

## Communications Functional Characteristics

Section 3.4.1 and 3.4.2 describes the Communications functional
characteristics which exist between the Spacecraft and the EDBS. This is
dependent upon favorable radio line of sight conditions and when the
station antenna elevation angle is greater than 5 degrees (above the
local mask). The Spacecraft X-band downlink Broadcast modes are shown in
Table 3.4-1.

### Science Data Mode

Transmission from the Spacecraft to EBS of real time science and
engineering data on the I and Q channels will be at a total data rate of
15 Mbps. Science data shall be formatted in accordance with the
characteristics outlined in Section.4.2.

### Pseudo-Random Bit Stream (PRBS) Mode

PRBS test data will be generated in the Formatter Multiplexer Unit (FMU)
of the C&DH subsystem and sent to the X-band modulator on the I and Q
channels maintaining a total data rate of 15.Mbps. The PRBS test mode is
used for the purpose of bit error rate (BER) checking, as required. It
is not a normal X-band downlink service

[]{#__RefHeading___Toc450549054 .anchor}Table 3.4-1: X-band Broadcast
Downlink Modes

  ------------- ------------------------- -------------- ----------------------- --
  **Mode**      **Description**           **I/Q Data     **Data Type**           
                                          Rate                                   
                                          \[Mbps\]**                             

  DB            Direct Broadcast          7.5 / 7.5      All real-time S&E data  
                (worldwide)                                                      

  TB            Test Broadcast            7.5 / 7.5      PRBS                    

  S&E: Science                                                                   
  and                                                                            
  Engineering                                                                    

  PRBS: Pseudo                                                                   
  Random Bit                                                                     
  Stream                                                                         
  ------------- ------------------------- -------------- ----------------------- --

# LINK INTERFACE CHARACTERISTICS

This section describes the functional design of the RF Direct Broadcast
link. Spacecraft and EDBS communications system performance and signal
characteristics are also described.

## Link Functional Design

### Spacecraft to Ground Station Design

The X-band section provides the downlink interface for both the Direct
Broadcast and Direct Broadcast Test modes. For EDBS support of the EOS
AQUA mission, the Direct Broadcast link will be utilized to transmit
real time science and engineering data to the ground stations.
Therefore, Pseudo-Random Bit Stream (PRBS) test data transmission will
be used only for bit error rate performance checking. In other words,
when the PRBS test mode is on, the Direct Broadcast mode will be off.

[]{#__RefHeading___Toc450549027 .anchor}Figure 4.1-1: Spacecraft-to-EDBS
Ground Station Downlink Configuration

### Spacecraft to Ground Station Functional Description

The functional interface of this link is shown in Figure 4.1-1. EBS
configuration is shown for information purposes only. On the Spacecraft,
data from the Formatter Multiplexer Unit (FMU) in the C&DH subsystem is
processed in real time at 15 Mbps. It is bit interleaved into two
streams of 7.5 Mbps (one for the I-channel and one for the Q-channel)
and sent to the X-band modulators. Each data stream is sent using the
Non-Return to Zero Mark (NRZ-M) format. In the PRBS test mode, the data
is a PRBS. This is generated in the FMU and sent also via NRZ-M format
on the I and Q channels at a rate of 7.5 Mbps each.

Irrespective of the transmission mode selected, the I and Q channel data
is Staggered Quadrature Phase Shift Keying (SQPSK) modulated onto the
X-band carrier with an I/Q channel power ratio of 1-to-1. The Q-channel
data is modulated on the Q-carrier which is delayed by 90 degrees with
respect to the I-channel data carrier. The I-channel and Q-channel
staggered data relationship is such that the Q-channel data is delayed
by 0.5 ± 0.1 symbol with respect to the I-channel data. The X-band
carrier at a frequency of 8160 MHz is derived from an internal
oscillator in the modulator. The traveling wave tube amplifier (TWTA)
performs amplification of the SQPSK signal received from the modulator
to the nominal saturated output power of 25 Watts (23 Watts EOL minimum)
for data transmission. The X-band filters suppress harmonic components
and out-of-band emissions from the TWTAs, and also suppress the portion
of the X-band spectrum falling within the Deep Space Research 8.4 to
8.45 GHz frequency band. The link uses the RHC polarized earth coverage
antenna to transmit the signal to EDBS.

As illustrated in Figure 4.1-1, once the input signal at the EBS antenna
is received, it is downconverted before being input to the SQPSK
receiver/demodulator. A separate tracking receiver may be utilized for
antenna auto-tracking purposes. The SQPSK receiver/demodulator
demodulates the downconverted signal into separate I and Q channel data
streams. Following QPSK demodulation, the bit synchronizers recover bit
clock. The 7.5 Mbps I and Q channels Broadcast data stream may then be
combined into one single stream of 15 Mbps. For the PRBS test mode, the
data may be provided to a BER test set for BER performance testing.

## Signal Characteristics and Constraints

This section provides a description of the signal characteristics and
constraints of the X-band downlink signal to the EBS.

### Science Frame Format

The science and engineering data transmitted via Direct Broadcast will
be formatted for transmission at 15 Mbps over the X-band link as
specified in D22262 (Interface Control Document between the EOS AQUA
Spacecraft and the EOS Ground System). See Figure 4.2-1 for the downlink
transfer frame format.

![](media/image6.wmf){width="5.916666666666667in"
height="1.7916666666666667in"}

[]{#__RefHeading___Toc450549028 .anchor}Figure 4.2-1: Channel Access
Data Unit (Sync + coded VCDU)

#### Reed-Solomon Coding

To provide improved bit error performance, the downlink data will have a
(255,223) Reed-Solomon code with interleave depth I = 4.

#### Bit Transition Generator

> a\. The pseudo-random bit stream (PRBS) is generated by the Spacecraft
> using the following bit transition generation function (refer to CCSDS
> 101.0 B-3 \"Telemetry Channel Coding\" Blue Book, May 1992, pp. 6-1):

h(x) = x^8^ + x^7^ + x^5^ + x^3^ + 1

> b\. This bit sequence repeats after 255 bits and the randomizer is
> reinitialized to an all-ones states during each Synchronization Marker
> period. The first 40 bits of the pseudo-random bit stream are shown
> below: the left-most bit is the first bit of the sequence and is
> exclusively ORed with the first bit of the CVCDU.

1111 1111 0100 1000 0000 1110 1100 0000 1001 1010

### Signal Characteristics

The Spacecraft X-band downlink signal characteristics are contained in
Table 4.2-1. As noted, the Balanced SQPSK modulated signal (channel
power ratio of 1-to-1) is radiated using a RHC polarized (Earth
Coverage) antenna on the Spacecraft.

[]{#__RefHeading___Toc450549055 .anchor}Table 4.2-1: X-band Downlink
Signal Characteristics

+-------------------------------------+--------------------------------+
| **Parameter**                       | **Requirement**                |
+-------------------------------------+--------------------------------+
| Center Frequency                    | 8160 MHz                       |
+-------------------------------------+--------------------------------+
| Bandwidth (1^st^ null-to-1^st\\^    | 15 MHz\*                       |
| null)                               |                                |
+-------------------------------------+--------------------------------+
| Data Modulation                     | SQPSK                          |
+-------------------------------------+--------------------------------+
| Data Format                         | NRZ-M                          |
+-------------------------------------+--------------------------------+
| I/Q Power ratio                     | 1 : 1                          |
+-------------------------------------+--------------------------------+
| Operational Duty Cycle              | 100%                           |
+-------------------------------------+--------------------------------+
| Antenna Coverage from nadir         | ±63.8°                         |
+-------------------------------------+--------------------------------+
| Antenna Polarization                | RHCP                           |
+-------------------------------------+--------------------------------+
| Data Rate                           | 15 Mbps                        |
+-------------------------------------+--------------------------------+
| Coding                              | Reed-Solomon (255-223)         |
|                                     |                                |
|                                     | (No Convolutional Coding)      |
+-------------------------------------+--------------------------------+
| \* Channel bandwidth ≈150 MHz       |                                |
+-------------------------------------+--------------------------------+

#### Data Signal Format

The science data signal output from the FMU of the C&DH subsystem is in
NRZ-M signal format prior to the modulator. The format for NRZ-M data
shall conform to that shown in Figure 4.2-2.

![](media/image7.wmf)

[]{#__RefHeading___Toc450549029 .anchor}Figure 4.2-2: Digital Data
Signal Formats

#### Data Rate Accuracy

Accuracy of the Direct Broadcast 15 Mbps data rate is within ±1.8
Kbps.[]{#__RefHeading___Toc450548990 .anchor}

### Modulated Signal Constraints

The signal constraints of the X-band Direct Broadcast link are in
accordance with Table 4.2-2. The X-band carrier is SQPSK modulated using
the I and Q baseband signals.

Table 4.2-2: X-band Downlink Signal Constraints

+-------------------------------------------+--------------------------+
| **Parameter**                             | **Requirement**          |
+-------------------------------------------+--------------------------+
| Frequency Stability                       | ±0.003 × 10^-6^          |
|                                           |                          |
| a\) 1 second average                      | ±0.1 × 10^-6^            |
|                                           |                          |
| b\) 5 hour average                        |                          |
+-------------------------------------------+--------------------------+
| Phase Noise                               | ≤ 7.5° RMS               |
|                                           |                          |
| 10 to 100 Hz                              | ≤ 2.0° RMS               |
|                                           |                          |
| 100 to 1000 Hz                            | ≤ 2.0° RMS               |
|                                           |                          |
| 1000 to 1 MHz                             |                          |
+-------------------------------------------+--------------------------+
| Data Asymmetry @ 15 Mbps                  | ≤ 0.4 %                  |
+-------------------------------------------+--------------------------+
| I/Q Data rise/fall Time                   | ≤ 2.5 nanosec.           |
+-------------------------------------------+--------------------------+
| Data Bit Jitter                           | ≤ 5 %                    |
+-------------------------------------------+--------------------------+
| I/Q Data Skew (Q delayed 0.5 bit)         | 0.5 ± 0.1 bit            |
+-------------------------------------------+--------------------------+
| SQPSK Amplitude Imbalance                 | ≤ 0.5 dB p-p             |
+-------------------------------------------+--------------------------+
| SQPSK Phase Imbalance                     | ≤ 4° ..                  |
+-------------------------------------------+--------------------------+
| SQPSK Carrier Suppression                 | 30 dBc                   |
+-------------------------------------------+--------------------------+
| Gain Slope†                               | 0.2 dB/MHz               |
+-------------------------------------------+--------------------------+
| AM/PM                                     | ≤ 5°/dB                  |
+-------------------------------------------+--------------------------+
| Spurious PM                               | \< 2° RMS                |
+-------------------------------------------+--------------------------+
| Gain Flatness‡                            | \< 2.0 dB p-p            |
+-------------------------------------------+--------------------------+
| Phase Nonlinearity‡                       | \< 12° p-p               |
+-------------------------------------------+--------------------------+
| † Over 150 MHz bandwidth centered at 8160 |                          |
| MHz                                       |                          |
+-------------------------------------------+--------------------------+
| ‡ Over 15 MHz centered at 8160 MHz        |                          |
+-------------------------------------------+--------------------------+

#### Downlink Frequency

The Spacecraft X-band downlinks use a single fixed frequency reference
for the transmit carrier. The frequency reference source is generated by
an internal oscillator. The carrier frequency derived from the
oscillator is 8160 MHz within the 8025-8400 MHz bandwidth. The frequency
characteristics of the oscillator are given below.

#### Downlink Frequency Stability

The frequency stability of the oscillator will be equal to or better
than the value specified in Table 4.2-2. Long term stability will be
less than ±2×10^-6^/YR and the initial set tolerance will be less than
±2×10^-6^. Over a -20°C to +60°C temperature range the stability will be
less than ±6×10^-6^.

#### Phase Noise

The carrier phase noise will be equal or better than the values
specified in Table 4.2-2.

## Downlink Acquisition and Tracking

### EDBS Station Characteristics

The EDBS station parameters need to be better than or equal to the G/T
values shown in Table 4.3-1 to insure the specified BER performance.

[]{#__RefHeading___Toc450549057 .anchor}Table 4.3-1: X-band EOS Direct
Broadcast Station G/T Values

+---------------------------------+------------------------------------+
| > Elevation                     | EDBS Ground Station G/T            |
+---------------------------------+------------------------------------+
| > \[deg.\]                      | \[dB/K\]                           |
+---------------------------------+------------------------------------+
| > 5°                            | 21.0                               |
+---------------------------------+------------------------------------+
| > 40°                           | 22.5                               |
+---------------------------------+------------------------------------+
| > 70°                           | 22.7                               |
+---------------------------------+------------------------------------+
| > 90°                           | 23.4                               |
+---------------------------------+------------------------------------+

**Appendix A**

**LINK CALCULATIONS**

Table A-: Broadcast Link Margin Summary

+----------------------------------+-----------------+-----------------+
| Ground Elevation                 | Nominal Margin  | Adverse         |
|                                  | \[dB\]          |                 |
|                                  |                 | Margin \[dB\]   |
+----------------------------------+-----------------+-----------------+
| 5° elevation \<=\> 63.8°         | 5.7             | 4.8             |
| off-Nadir                        |                 |                 |
+----------------------------------+-----------------+-----------------+
| 71° elevation \<=\> 17°          | 4.6             | 2.6             |
| off-Nadir                        |                 |                 |
+----------------------------------+-----------------+-----------------+
| 90° elevation \<=\> 0° off-Nadir | 8.8             | 8.1             |
+----------------------------------+-----------------+-----------------+

Table A-: Direct Broadcast Mode - 15 Mbps X-band Downlink Budget

+---+-------------------+-----+-----+-----+------+--------+-------------+
|   | Parameter         | R   |     |     | U    | A      | Items in    |
|   |                   | esu |     |     | nits | dverse |             |
|   |                   | lts |     |     |      |        |             |
|   |                   | at  |     |     |      | Tol    |             |
|   |                   | off |     |     |      | erance |             |
|   |                   | -na |     |     |      |        |             |
|   |                   | dir |     |     |      |        |             |
|   |                   | a   |     |     |      |        |             |
|   |                   | ngl |     |     |      |        |             |
|   |                   | es, |     |     |      |        |             |
|   |                   | θ   |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
|   |                   | 63  | 17° | 0°  |      | (dB)   | Table A-3   |
|   |                   | .8° |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 1 | TWTA Tx Output    | 1   | 1   | 1   | dBW  | 0.4    | Item 2      |
| \ | Power             | 4.0 | 4.0 | 4.0 |      |        |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 2 | Transmit Circuit  | -   | -   | -   | dB   | 0.2    | Item 3      |
| \ | loss              | 3.0 | 3.0 | 3.0 |      |        |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 3 | Antenna loss/gain | 6.8 | -   | -   | dBi  | 0.5,1  | Item 4 a,   |
| \ |                   |     | 7.2 | 4.1 |      | .6,0.3 | b, &, c     |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 4 | EOS EIRP          | 1   | 3.8 | 6.9 | dBWi |        | Σ           |
| \ |                   | 7.8 |     |     |      |        |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
|   |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 6 | Space loss/gain   | -17 | -16 | -16 | dB   | \-     | Item 6 a,   |
| \ |                   | 8.9 | 8.1 | 7.6 |      |        | b, &, c     |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 7 | Atmospheric       | -   | 0.0 | 0.0 | dB   | \-     | Item 7 a,   |
| \ | loss/gain         | 0.5 |     |     |      |        | b, &, c     |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
|   |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 9 | Polarization      | -   | -   | -   | dB   | 0.6,1  | Item 9      |
| \ | loss/gain         | 0.4 | 0.5 | 0.6 |      | .2,0.4 |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 1 | Received          | -16 | -16 | -16 | dBWi |        | Σ           |
| 0 | isotropic power   | 2.0 | 4.8 | 1.3 |      |        |             |
| \ |                   |     |     |     |      |        |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
|   |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 1 | User Ground       | 2   | 2   | 2   | d    | \-     | Item 10 a,  |
| 1 | Terminal G/T      | 1.0 | 2.7 | 3.4 | Bi/K |        | b, &, c     |
| \ |                   |     |     |     |      |        |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 1 | 1/Boltzmann\'s    | 22  | 22  | 22  | dBH  | \-     | 1.          |
| 2 | constant          | 8.6 | 8.6 | 8.6 | zK/W |        | 38\*10\^-23 |
| \ |                   |     |     |     |      |        | W s / K     |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 1 | 1/Data rate       | -7  | -7  | -7  | dB-  | \-     | Item 11     |
| 3 |                   | 1.8 | 1.8 | 1.8 | sec. |        |             |
| \ |                   |     |     |     |      |        |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 1 | Received Eb/No    | 1   | 1   | 1   | dB   |        | Σ           |
| 4 |                   | 5.8 | 4.7 | 8.9 |      |        |             |
| \ |                   |     |     |     |      |        |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
|   |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 1 | Implementation    | -   | -   | -   | dB   | \-     | Item 12†    |
| 5 | loss/gain         | 3.3 | 3.3 | 3.3 |      |        |             |
| \ |                   |     |     |     |      |        |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 1 | Required Eb/No    | -   | -   | -   | dB   | \-     |             |
| 6 |                   | 6.8 | 6.8 | 6.8 |      |        |             |
| \ |                   |     |     |     |      |        |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
|   |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 1 | Nominal link      | 5.7 | 4.6 | 8.8 | dB   |        |             |
| 7 | margin            |     |     |     |      |        |             |
| \ |                   |     |     |     |      |        |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+
|   | Adverse tolerance | -   | -   | -   | dB   | 0.9,2  | Adverse     |
|   |                   | 0.9 | 2.0 | 0.7 |      | .0,0.7 | Tolerance   |
+---+-------------------+-----+-----+-----+------+--------+-------------+
| 1 | Adverse link      | 4.8 | 2.6 | 8.1 | dB   |        | Margin less |
| 8 | margin            |     |     |     |      |        | adv. tol.   |
| \ |                   |     |     |     |      |        |             |
| . |                   |     |     |     |      |        |             |
+---+-------------------+-----+-----+-----+------+--------+-------------+

Note: End-to-end data rate refers to the 15 Mbps data stream at input to
Reed-Solomon decoder

† Implementation loss is an estimate of spacecraft constraint loss plus
ground station signal processing loss, individual user ground station
loss could be higher.

Table A-: X-band Downlink Budget - Parameters

  ---------------- ---------------------- -------- -------- ------ ---------------------------- --
                   Parameter              Units    Value    Adv.   Comments                     

  **1.**           Frequency              GHz      8.1600          Selected frequency in        
                                                                   8.025 - 8.400 GHz band       

  **2.**           TWTA Transmit Output   dBW      14.0     0.4    25W nominal, 23W spec.       
                   Power                                                                        

  **3.**           Transmit Circuit       dB       3.0      0.2    Current measurement          
                   Losses                                                                       

  **4.**           Antenna Gain                                                                 

                   \(a\) 5° elev. \<=\>   dBi      6.8      0.5    Measurements, avg. (SN301    
                   63.8° off-Nadir                                 Antenna)                     

                   \(b\) 71° elev. \<=\>  dBi      -7.2     1.6                                 
                   17° off-Nadir                                                                

                   \(c\) 90° elev. \<=\>  dBi      -4.1     0.3                                 
                   0° off-Nadir                                                                 

  **6.**           Space Loss                                      From EOS to X-band ground    
                                                                   terminal                     

                   \(a\) 5° elevation     dB       178.9           Range at 2574 km. is maximum 
                   angle                                           range                        

                   \(b\) 71° elevation    dB       168.1           Range at 741 km.             
                   angle                                                                        

                   \(c\) 90° elevation    dB       167.6           Range at 705 km.             
                   angle                                                                        

  **7.**           Atmospheric loss                                For Direct Playback and      
                                                                   Direct Broadcast             

                   \(c\) 5° elevation     dB       0.50            Clear air atmospheric using  
                   angle                                           CCIR Specific Model          

                   \(b\) 71° elevation    dB       0.05                                         
                   angle                                                                        

                   \(a\) 90° elevation    dB       0.05                                         
                   angle                                                                        

                   Ground temperature     deg C    22.0            CCIR Specific Model: ground  
                                                                   station temp.                

                   Water Vapor Density    g/m^3^   7.5             CCIR Specific Model: water   
                                                                   vapor density                

                   Earth Terminal         km       0.0             CCIR Specific Model: alt.    
                   Altitude                                        above mean sea level         

  **8.**           Rain Loss                                       For Direct Playback only     
                                                                   (Using Crane model)          

                   \(a\) 5° elevation     dB       0.00            95% avail. & climate A       
                   angle                                           (99.7% =\> 0.06 dB)          

                   \(b\) 71° elevation    dB       0.00            95% avail. & climate A       
                   angle                                                                        

                   \(c\) 90° elevation    dB       0.00            95% avail. & climate A       
                   angle                                                                        

                                                                                                

  **9.**           Polarization Loss      dB                                                    

                   Ground Terminal Rx     dB                       Estimate                     
                   Axial Ratio (1.8)                                                            

                   S/C Transmit Axial                              AR Measurements, avg. (SN    
                   Ratio:                                          301 Antenna)                 

                   63.8° (4.9)            dB       0.4      0.6                                 

                   17° (5.7)              dB       0.5      1.2                                 

                   0° (6.7)               dB       0.6      0.4                                 

  **10.**          User Ground Station                                                          
                   G/T                                                                          

                   \(a\) 5° elevation     dBi/K    21.0            Direct Broadcast (15 Mbps)   
                   angle                                           §4.3.5.10†                   

                   \(b\) 71° elevation    dBi/K    22.7            \^Temperature increase due   
                   angle                                           to rain is 0 dB              

                   \(c\) 90° elevation    dBi/K    23.4                                         
                   angle                                                                        

  **11.**          CCSDS data rate                                                              

                   15 Mbps                dB-Hz    71.8                                         

  **12.**          Other losses                                                                 

                   Differential Decoding           0.3             NRZ-M                        
                   Loss                                                                         

                   Minimum Implementation dB       3.0             From §4.3.5.11† (DP) and     
                   Loss                                            §4.3.5.10† (DB)              

                   Total                  dB       3.3                                          

  **13.**          Required Eb/No                                  10\^-3 BER per §4.3.5.8†     

                   Ideal required Eb/No   dB       6.8             Ideal PSK (no coding);       
                                                                   CCSDS700.0 G-3 Pg. A-5       

  † EOS AQUA                                                                                    
  Common                                                                                        
  Spacecraft                                                                                    
  Specification:                                                                                
  GSFC                                                                                          
  422-13-11-01                                                                                  
  ---------------- ---------------------- -------- -------- ------ ---------------------------- --

**Appendix B**

**X-BAND EARTH COVERAGE ANTENNA PATTERN**

![](media/image8.wmf)

Figure B-1: EOS Aqua X-band EC Antenna (S/N 301) Gain Performance