> **INTERFACE DESCRIPTION DOCUMENT**
>
> **FOR**
>
> **EOS AQUA X-BAND DIRECT BROADCAST**
>
> **EOS AQUA PROJECT**
>
> **JUNE 2002**

![](media/image1.wmf){width="5.75in" height="1.125in"}

> INTERFACE DESCRIPTION DOCUMENT
>
> FOR
>
> EOS AQUA X-BAND DIRECT BROADCAST

EOS AQUA PROJECT

> June 2002
>
> NASA Goddard Space Flight Center
>
> Greenbelt, Maryland
>
> INTERFACE DESCRIPTION DOCUMENT
>
> FOR
>
> EOS AQUA X-BAND DIRECT BROADCAST

EOS AQUA PROJECT

Based on: TRW Document D26699, Rev. B, Dated March 25, 2002

Modified By: \_\_\_\_*[\_C.
Wu]{.underline}*\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

C. Wu

EOS Aqua Systems Manager

Approved By: \_\_\_\_\_*[M. Donnelly
for]{.underline}*\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

EOS Aqua Project Manager

CHANGE RECORD PAGE

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EOS 420-CM-04 (4/92)

**Table of Contents**

1\. INTRODUCTION [1](#__RefHeading___Toc450548956)

1.1 SCOPE 1

1.2 OVERVIEW 1

1.3 LINK CALCULATIONS 2

1.4 DATA CONTENTS AND FORMATS 2

2\. REFERENCE DOCUMENTS [3](#reference-documents)

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

3.1 SPACECRAFT TO GROUND STATION FUNCTIONAL DESIGN 4

3.2 Signal Characteristics and Constraints
[5](#signal-characteristics-and-constraints)

3.2.1 Science Frame Format [5](#__RefHeading___Toc450548984)

3.2.1.1 Reed-Solomon Coding [6](#reed-solomon-coding)

3.2.2 Signal Characteristics [6](#signal-characteristics)

3.2.2.1 Data Signal Format [7](#__RefHeading___Toc450548988)

3.2.2.2 Data Rate Accuracy [7](#data-rate-accuracy)

3.2.3 Modulated Signal Constraints [8](#__RefHeading___Toc450548990)

3.2.3.1 Downlink Frequency Stability [8](#downlink-frequency-stability)

3.2.3.2 Phase Noise 8

3.2.4 Bit Error Rate 9

3.3 DBGS STATION CHARACTERISTICS 9

Appendix A: Link Calculations ...\... ..10

Appendix B: X-band EARTH COVERAGE Antenna Pattern 14

**List of Figures**

Figure 1.2-1: X-band Direct Broadcast Downlink
[1](#__RefHeading___Toc450549025)

Figure 3.1-1: Spacecraft-to-DBGS ground station downlink configuration
[5](#__RefHeading___Toc450549027)

Figure 3.2-1: Channel Access Data Unit (Sync + coded VCDU)
[6](#__RefHeading___Toc450549028)

Figure 3.2-2: Digital data Format [7](#__RefHeading___Toc450549029)

Figure B-1: EOS aqua x-band earth coverage antenna (s/n 301) gain
performance 15

**List of Tables**

Table 3.2-1: X-band Downlink Signal Characteristics
[7](#__RefHeading___Toc450549055)

Table 3.2-2: X-band DB Downlink Signal constraints 8

Table 3.3-1: X-band EOS Direct Broadcast ground Station g/t
[9](#__RefHeading___Toc450549057)

Table A-1: direct broadcast link margin summary 11

Table A-2: 15 Mbps X-band Direct Broadcast Downlink Budget 12

Table A-3: X-band DB Downlink Budget - Parameters 13

[]{#__RefHeading___Toc450548956 .anchor}**[1.]{.smallcaps}
INTRODUCTION**

## Scope

This Interface Description Document (IDD) describes the Direct Broadcast
(DB) radio frequency interface between the EOS AQUA spacecraft and the
worldwide Earth Observing System (EOS) Direct Broadcast Ground Stations
(DBGS), which receive real time science and engineering data via X-band
DB service. Source of information for the DB data content and structure
is also provided.

## OVERVIEW

EOS Aqua, formerly known as EOS-PM-1, is the second of the NASA EOS
missions. It carries AIRS, AMSR-E, AMSU-A, CERES, HSB and MODIS
instruments.

In the Direct Broadcast mode the Aqua spacecraft continuously transmits
all real-time instrument science data, real-time spacecraft engineering
(housekeeping) data, instrument engineering (housekeeping) data and
ground-based attitude determination (GBAD) data as it travels in a
sun-synchronous near circular orbit at a nominal altitude of 705 km
(Figure 1.2-1). The data rate is 15 Mbps at a nominal downlink frequency
of 8160 MHz. In normal operations the Direct Broadcast mode will be on
during most of the 99 minute orbit. It is off briefly when the
spacecraft is in Playback mode, playing back data stored in the onboard
solid state recorder to one of the four Earth Observing System Polar
Ground Stations (EPGS) located at Poker Flat, Alaska and Svalbard,
Norway.

![](media/image2.wmf)

[]{#__RefHeading___Toc450549025 .anchor}Figure 1.2-1 X-band Direct
Broadcast Downlink

### 1.3 Link Calculations {#link-calculations .unnumbered}

The RF link calculations and the X-band earth coverage antenna pattern
data are provided in Appendix A and Appendix B respectively.

## Data Contents and Formats

The contents and formats of the DB data are described in Section 5 and
Appendix B of Reference Document 2a, EOS PM-1 Spacecraft to EOS Ground
System Interface Control Document. It should be pointed out that the
GBAD data includes not only the data for ground attitude determination
but also a selected subset of spacecraft and instrument housekeeping
data useful for science data analysis.

# REFERENCE DOCUMENTS

> a\. GSFC 422-11-19-03: EOS PM-1 Spacecraft to EOS Ground System
> Interface Control Document, Revision A, March 2002.
>
> b\. 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.
>
> c\. CCSDS 101.0 B-3: Telemetry Channel Coding, Blue Book, May 1992.

# LINK INTERFACE CHARACTERISTICS

This section describes the functional design of the RF Direct Broadcast
link, spacecraft and DBGS communications system performance and signal
characteristics.

## Spacecraft to Ground Station functional Design

The functional interface of this link is shown in Figure 3.1-1. DBGS
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. The data is Reed-Solomon coded as
described in 3.2.1.1 and CCSDS randomized as described in 3.2.1.2.
Randomization can be commanded off if desired. The Reed-Solomon coded
and randomized data is then 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 case of a bit error rate (BER) test, the data is
a Pseudo-Random Bit Stream (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.

The I and Q channel data is then 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 I-channel bit is the first bit of an I/Q data bit
pair. 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
End-of-Life 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 Right
Hand Circular Polarization (RHCP) earth coverage antenna to transmit the
signal to DBGS. Across a 63.8 degree half cone angle the reflector is
shaped to provide approximately constant power density to any DB ground
station with line-of-sight view as the spacecraft passes overhead.

As illustrated in Figure 3.1-1, once the input signal at the DBGS
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 SQPSK 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. Again, the I-channel bit
leads the Q-channel bit and is the first bit of an I/Q data bit pair.
The data must be de-randomized and Reed-Solomon decoded. In the case of
a BER test, the data may be provided to a BER test set.

> []{#__RefHeading___Toc450549027 .anchor}Note:
>
> The 15 Mbps output from the bit deinterleaver needs to be
> de-randomized and Reed-solomon decoded

Figure 3.1-1 Spacecraft-to-DBGS Ground Station Downlink Configuration

## 3.2 Signal Characteristics and Constraints {#signal-characteristics-and-constraints .unnumbered}

This section provides a description of the signal characteristics and
constraints of the X-band downlink signal to the
DBGS.[]{#__RefHeading___Toc450548984 .anchor}

### 3.2.1 Science Frame Format {#science-frame-format .unnumbered}

The science and engineering data transmitted via Direct Broadcast will
be formatted for transmission at 15 Mbps over the X-band link as
described in Section 5 of Reference Document 2a, EOS PM-1 Spacecraft to
EOS Ground System Interface Control Document. See Figure 3.2-1 for the
downlink Channel Access Data Unit format.

![](media/image3.wmf){width="5.916666666666667in"
height="1.7916666666666667in"}

[]{#__RefHeading___Toc450549028 .anchor}Figure 3.2-1 Channel Access Data
Unit (Sync + coded VCDU)

#### 3.2.1.1 Reed-Solomon Coding {#reed-solomon-coding .unnumbered}

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

#### 3.2.1.2 Data Randomization {#data-randomization .unnumbered}

> a\. The pseudo-random bit stream (PRBS) is generated by the Spacecraft
> using the following bit transition generation function (refer to
> Reference Document 2c, 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 coded VCDU, i.e. the entire
> CADU is thus randomized except for the 32-bit Sync Marker,

1111 1111 0100 1000 0000 1110 1100 0000 1001 1010

### 3.2.2 Signal Characteristics {#signal-characteristics .unnumbered}

The Spacecraft X-band downlink signal characteristics are provided in
Table 3.2-1. 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 3.2-1 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       |                                |
+-------------------------------------+--------------------------------+

[]{#__RefHeading___Toc450548988 .anchor}

#### 3.2.2.1 Data Format {#data-format .unnumbered}

The science data output from the FMU of the C&DH subsystem is in NRZ-M
data format prior to the modulator. The I and Q channels are separately
NRZ-M coded. The format for NRZ-M data is shown in Figure 3.2-2.

![](media/image4.wmf)

> []{#__RefHeading___Toc450549029 .anchor}Figure 3.2-2 Digital Data
> Format

#### 3.2.2.2 Data Rate Accuracy {#data-rate-accuracy .unnumbered}

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

### 3.2.3 Modulated Signal Constraints {#modulated-signal-constraints .unnumbered}

The signal constraints of the X-band Direct Broadcast link are in
accordance with Table 3.2-2. The X-band carrier is SQPSK modulated using
the I and Q baseband signals.

> **Table 3.2-2 X-band DB 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        |                          |
+-------------------------------------------+--------------------------+

#### 3.2.3.1 Downlink Frequency Stability {#downlink-frequency-stability .unnumbered}

#### 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-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. .unnumbered}

The frequency stability of the oscillator will be equal to or better
than the value specified in Table 3.2-2. 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^.

#### 3.2.3.2 Phase Noise {#phase-noise .unnumbered}

The carrier phase noise will be equal or better than the values
specified in Table 3.2-2.

### 3.2.4 Bit Error Rate {#bit-error-rate .unnumbered}

### The X-band downlink BER for the detected digital science data in the data channel will be ≤10^-3^, at the input of a Reed-Solomon Decoder on the ground. 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-x-band-downlink-ber-for-the-detected-digital-science-data-in-the-data-channel-will-be-10-3-at-the-input-of-a-reed-solomon-decoder-on-the-ground.-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. .unnumbered}

### 3.3 DBGS Station Characteristics {#dbgs-station-characteristics .unnumbered}

To ensure the specified BER performance the DBGS station parameters need
to be better than or equal to the G/T values shown in Table 3.3-1.

[]{#__RefHeading___Toc450549057 .anchor}Table 3.3-1 X-band EOS Direct
Broadcast Ground Station G/T

+---------------------------------+------------------------------------+
| > Elevation                     | DBGS 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- Direct 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- 15 Mbps X-band Direct Broadcast 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 DB 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/image5.wmf)

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