Janette C. Briones and Mary Jo Shalkhauser

Glenn Research Center, Cleveland, Ohio

General Dynamic (GD) Launch Waveform On-Orbit 

Performance Report 

NASA/TM—2014-218316

December 2014
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Janette C. Briones and Mary Jo Shalkhauser

Glenn Research Center, Cleveland, Ohio

General Dynamic (GD) Launch Waveform On-Orbit 

Performance Report 

NASA/TM—2014-218316

December 2014

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135
Available from

NASA STI Information Desk

Mail Stop 148

NASA Langley Research Center

Hampton, VA 23681-2199

National Technical Information Service

5301 Shawnee Road

Alexandria, VA 22312

Available electronically at http://www.sti.nasa.gov

Level of Review: This material has been technically reviewed by technical management. 
NASA/TM—2014-218316 1 

General Dynamic (GD) Launch Waveform On-Orbit 

Performance Report 

Janette C. Briones and Mary Jo Shalkhauser 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Abstract 

The purpose of this report is to present the results from the GD SDR on-orbit performance testing 

using the launch waveform over TDRSS. The tests include the evaluation of well-tested waveform modes, 

the operation of RF links that are expected to have high margins, the verification of forward return link 

operation (including full duplex), the verification of non-coherent operational models, and the verification 

of radio at-launch operational frequencies. This report also outlines the launch waveform tests conducted 

and comparisons to the results obtained from ground testing. 

Introduction 

The objective of the Space Communications and Navigation (SCaN) Testbed is to investigate the 

applicability of software defined radios (SDR) to NASA missions and to study the operation of SDRs and 

their waveform applications in an operational space environment. Developed at NASA’s Glenn Research 

Center, the SCaN Testbed is an experimental communication system that provides the capability for 

S-Band, Ka-Band, and L-Band communication with both space and ground assets. The SCaN Testbed 

was launched on July 20, 2012, and is installed on the International Space Station (ISS) (Fig. 1). The 

SCaN Testbed contains three SDRs which are reprogrammable and are running waveform applications 

that enable reconfigurability. The testbed provides experimenters an opportunity to develop and 

demonstrate experimental waveforms in space to reduce cost and risk for future space missions using 

SDRs, and to develop and test experimental waveforms. 

One of the radios was developed by General Dynamics (GD) (Fig. 2). The GD SDR is an S-Band 

Tracking Relay Data Satellite System (TDRSS) fourth-generation transponder. The GD SDR supports 

full-duplex communications at S-band frequency. The S-band capabilities of the radio have been tested 

with NASA’s Tracking and Data Relay Satellite System (TDRSS) network of geosynchronous satellites. 

The GD SDR launch waveform was installed on the GD SDR prior to launch to ISS. This waveform 

is compliant with the capabilities of TDRSS and allows the radio to support full-duplex communication 

with a Tracking and Data Relay Satellite (TDRS). The waveform is compliant with the Space 

Telecommunications Radio System (STRS) architecture standard. 

Prior to the launch of the SCaN Testbed, an extensive set of communications tests was performed 

with the GD SDR for the verification of application requirements and for SDR characterization. These 

tests included functional and performance testing of the engineering model (EM) and the flight model 

(FM) versions of the GD SDR. These tests were performed at the Glenn Research Center (GRC), and 

included vibration tests, thermal vacuum (TVAC) tests, and electromagnetic interference (EMI) tests. The 

GD SDR Data Book (SCaN Testbed project document GRC-CONN-RPT-0917) details the results of the 

GD launch waveform performance during ground testing. This set of performance data will be used as a 

baseline for evaluating the on-orbit performance of the radio. 
NASA/TM—2014-218316 2 

Figure 1.—SCaN Testbed Installed on ISS. 

Figure 2.—GD Software Defined Radio. 

TABLE 1.—GD SDR RECEIVE WAVEFORM DESCRIPTION 

Waveform Number Center Frequency Data Rate

(kbps)

Forward Error Correction (FEC)

180/182 SA 18 Uncoded

179/181 SA 18 Coded

184/186 MA 18 Uncoded

183/185 MA 18 Coded

204/206 SA 72 Uncoded

203/205 SA 72 Coded

208/210 MA 72 Uncoded

207/208 MA 72 Coded

The GD SDR receive waveform includes several reconfigurable parameters which include data rate, 

coding enable/disable, and center frequency. The receive waveform is a spread signal and is compatible 

with the Tracking Relay Data Satellite System (TDRSS). The S-Band RF center frequency can be 

changed to operate with the TDRSS Single Access (SA) or Multiple Access (MA) modes. The receive 

waveform also can be configured to operate at 18 kbps or 72 kbps data rates. The Viterbi decoder for 

forward error correction decoding can be enabled and disabled. These three parameters lead to the eight 

receive waveform combinations as shown in Table 1. For the SCaN Testbed operations, a unique transmit 

and receive waveform configuration was given a unique waveform number. 

The purpose of this report is to present the results from the GD SDR on-orbit performance testing 

using the launch waveform over TDRSS. The tests include the evaluation of well-tested waveform modes, 

the operation of RF links that are expected to have high margins, the verification of forward/return link 

operation (including full duplex), the verification of non-coherent operational models, and the verification 

of radio at-launch operational frequencies. This report also outlines the launch waveform tests conducted 

and comparisons to the results obtained from ground testing. 
NASA/TM—2014-218316 3 

GD Launch Waveform On-Orbit Tests 

Launch waveform characterization test were designed to understand the performance of the GD SDR 

in a flight environment. Variations of the tests were used to test the medium gain antenna (MGA) path, 

the single access (SA) and multiple access (MA) frequencies, coded and uncoded data, a variety of data 

rates, and non-coherent waveforms. During Launch Waveform Testing, 23 TDRSS events were 

conducted. The selected waveform configurations were chosen to exercise a variety of the waveform’s 

reconfigurable parameters and to give the best performance (i.e., the waveforms with the best link 

margins). Table 2 shows a list of the test events using the launch waveform in an operational environment 

with the best performing waveforms. 

A full list of the launch waveform test performed including full system and waveform configuration 

and test objectives can be found in Table 7, Launch Waveform Test Matrix, in Appendix A. The mission 

operations team used these tables to generate their operational procedures and schedule events with the 

space network (SN). 

During the commissioning phase of on-orbit tests, the GD SDR was operated under typical missionlike antenna pointing and power conditions. Twenty-seven TDRSS events were completed. During these 

tests the RF link margins were verified and found to be performing as expected, according to the GD 

Space Network Link Book described in the GD SDR Commissioning Report (SCaN Testbed project 

document GRC-CONN-RPT-1020 APPENDIX C). 

All tested waveforms met or exceeded the expected bit error rate performance. A variety of 

waveforms were utilized so that all waveform characteristics (antenna, RF path, data rate, 

encoding/decoding, center frequency, internal BER, SpaceWire/Avionics BER, framing/deframing, etc.) 

could be tested on-orbit. All the TDRSS modes (DG1 modes 1, 2 and 3; and DG2) implemented in the 

GD radio were exercised. 

Every test was completed at least two times to verify that the results were repeatable. A summary of 

the waveform configurations for the commissioning tests and the test results are shown in Table 3. This 

summary table shows the expected BER performance and the BER performance demonstrated on-orbit. 

TABLE 2.—LAUNCH WAVEFORM TESTING EVENTS SUMMARY 

Test Antenna Freq. Links Coherent Forward 

Rate

Return Rate SpW FEC Status

Test 20 SN-MGA SA Full-Duplex No 18 k 24 k No No Passed

Test 21 SN-MGA MA Full-Duplex No 18 k 24 k Yes Yes Passed

Test 22 SN-MGA SA Full-Duplex Yes 72 k 192 k No No Passed

Test 23 SN-MGA MA Full-Duplex No 72 k 192 k Yes No Passed

TABLE 3.—COMMISSIONING AND LAUNCH WAVEFORM TESTING EVENTS SUMMARY

Antenna Freq. Links Coherent Forward 

Rate

Return 

Rate

SpWFEC Expected BER Actual BER Status

FWD RTN FWD RTN

Test 6 SN-MGA SA Full-duplex No 18 K 24 K No Yes 0 0 0 0 Passed

Test 7 SN-LGA MA Full-duplex No 18 K 24 K Yes No 6×10–3

8×10–34×10–54×10–4 Passed

Test 8 SN-MGA SA Full-duplex Yes 72 K 192 K No No 0 0 0 0 Passed

Test 8b SN-MGA SA Full-duplex Yes 72 K 1 M

DG1M3 No No 0 * 0 10–3 Passed

Test 8c SN-MGA SA Full-duplex No 72 K 1 M

DG2 No No 0 * 0 10–4 Passed

Test 9 SN-MGA MA Full-duplex Yes 72 K 192 K Yes No 0 * 0 ** Passed

Test 9b SN-MGA MA Full-duplex Yes 72 K 192 K No Yes 0 * 0 ** Passed

Test 10 SN-MGA SA Full-duplex Yes 72 K 192 K Yes Yes 0 0 0 0 Passed

*Not expected to acquire.

**Could not acquire.
NASA/TM—2014-218316 4 

All commissioning forward-link tests met or exceeded the expected performance. All SN-MGA forwardlink tests resulted in a bit error rate of zero, as expected, due to the high power at the input to the SDR. 

The SN-LGA forward-link, in contrast, had a much lower link margin and the SDR experienced bit errors 

in the data during the entire event (Test 7). Every test on the return-link met or exceeded the expected bit 

error rate performance. Table 3 shows that the return-link for the SA 24 kbps and 192 kbps events (Test 6, 

8, and 10) achieved a BER of zero over the duration of each event. Test 7, the SN-LGA event, achieved a 

4×10–4 BER averaged over the event length due to the lower gain and lower link margin. The high data 

rate (1 Mbps) events (Tests 8b and 8c) achieved an average BER of 10–3 and 10–4

, respectively. This BER 

was better than expected, since the link margin was not expected to be high enough to close the link. The 

two 192 kbps, MA events (test 9 and 9b) did not have enough power for the receiver at White Sands to 

acquire a signal and achieve a BER. 

Antenna Off-Pointing 

During launch waveform testing, full characterization of the on-orbit performance of the GD SDR 

required the radio to operate at power levels other than those typically provided by White Sands and the 

TDRSS spacecraft(s). A wide range of power levels at the input to the GD radio was desired in order to 

capture on-orbit data. The input power to the GD SDR was varied using purposeful antenna off-pointing 

allowing the experimenters to gather full BER curves, radio acquisition level data, and digital and analog 

automatic gain control (AGC) data. 

Early profiles as shown in Figure 3 were designed to start the input power level below the SDR 

acquisition level and raise it to the point where zero bit errors would be seen. Then the power would be 

lowered again past the point where the radio would be expected to lose acquisition. This style of profile 

worked well for acquiring BER data, but was not good for acquisition levels. The profiles were designed 

for 40 min TDRSS events, but the actual events often were as short as 20 to 30 min. 

During testing, it was determined that it was easier to find the point where the radio loses acquisition, 

rather than the point where it acquires. When the GD radio reaches state 5 in its acquisition state machine, 

it is acquired enough to receive data. It was difficult to know emphatically at the beginning of an event 

when the radio reached state 5 if it was because it just got the minimum amount of power to reach state 5, 

or if it had more than enough power and had to transition through all the states to reach state 5. 

Figure 3.—Profile Style 1.

-130

-128

-126

-124

-122

-120

-118

-116

-114

0 5 10 15 20 25 30 35 40

Input Power to SDR (dBm)

Time Relative to Start of Event (minutes)

Test 20 Pointing Error Profile
NASA/TM—2014-218316 5 

As the GD receiver acquires a signal, it progresses through a state machine with the 6 states whose 

functions are described in Table 4. 

All the TDRSS events using the profile style shown in Figure 3 were never long enough to reach a 

power low enough as shown in the second half of the profile in Figure 3 to lose acquisition during the 

second half of the profile. Figure 4 shows the actual achieved profile during one particular event. This 

figure shows the predicted power and the estimated power obtained during that event. 

TABLE 4.—RECEIVE WAVEFORM STATES 

Receive Waveform States Functions

1 – Search The SDR is searching for a RF input signal, but it does not see any power. The PN code is 

being swept to correlate with the received signal.

2 – AGC Normalization/PN 

Code Loop Acquisition

Both the digital and analog AGC gain is being set. During this state the code tracking loop is 

locking to the received short code.

3 – PN Code Lock 

Detection/Sidelobe Search

The receiver has begun tracking the short code and is now looking for the PN lock detector to 

indicate lock. At the same time, the SDR searches the PN code again for higher power on 

sidelobe, looking for a correlation with more signal energy. If one is found, the initial lock was 

to a sidelobe.

4 – PN Code 

Locked/Carrier Acquisition

The PN code is locked and the carrier is being acquired.

5 – Carrier Locked/Long 

Code Acquisition

The carrier is locked and the SDR is trying to acquire the long PN code. The bit sync will be 

locked in this state and BER measurements can be made.

6 – TDRSS Mode Tracking The carrier, PN code, and Long code are locked and the SDR is tracking.

Figure 4.—Estimated and predicted received power at SDR (Profile Style 1). 
NASA/TM—2014-218316 6 

Figure 5 shows the bit error rate curve obtained during the test shown in Figure 4. This style of 

pointing profile was designed to allow more time high power levels to obtain more accurate bit error rate 

data. 

In order to obtain expected acquisition data, the profile style was changed as shown in Figure 6. This 

profile started at high powers, where a zero BER was expected, and dropped quickly to power levels 

below where the radio can operate. This profile style generally was designed to the exact length of the 

actual TDRSS event. This approach resulted in good acquisition level data, but often poor BER data for 

higher powers, because not enough time was spent at the higher power levels to get accurate data. Figure 

7 shows the actually achieved estimated and predicted power into the SDR for an example event. 

Figure 5.—Bit error rate curve (Profile Style 1). 

Figure 6.—Profile Style 2. 

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 2 4 6 8 10 12

Bit Error Rate

Eb/No (dB)

Bit Error Rate - Test 20, Event 4 

Theoretical

TVAC Ground Test (-4 deg. C)

Flight Test 20 (6-9 deg. C)

-130

-128

-126

-124

-122

-120

-118

-116

0 5 10 15 20 25 30 35 40

Input Power to SDR (dBm)

Time Relative to Start of Event (min)

Test 20 Pointing Error Profile
NASA/TM—2014-218316 7 

Figure 7.—Estimated and predicted received power at the SDR (Profile Style 2). 

Figure 8.—Bit error rate curve (Profile Style 2). 

Figure 8 shows the BER curve achieved with this type of profile for that event. Notice that the BER 

curve spreads out at the higher Eb/N0 values. This is caused by the short amount of time spent in the 

higher power levels with this 2nd profile type. 

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 2 4 6 8 10 12 14

Bit Error Rate

Eb/No (dB)

Bit Error Rate -- Test 20, Event 7

Flight Test 20 (6-9 deg. C)

Theoretical

TVAC Ground Test (-4 deg. C)
NASA/TM—2014-218316 8 

SDR Input Power 

The input power to the GD SDR was estimated using the digital and analog AGC telemetry values 

measured during each test. The algorithm for the power estimate was designed and verified during ground 

testing of the GD flight model SDR prior to launch and installation of the SCAN Testbed on the ISS. 

Detailed information on this power estimator and performance in estimating the SDR input power can be 

found in the paper entitled SDR Input Power Estimator Algorithms presented (by Janette Briones and 

Jennifer Nappier) at the IEEE Aerospace Conference at Big Sky, Montana, March 2013. 

Figure 9 shows typical power levels seen at the input to the GD SDR during commissioning. 

Commissioning tests were designed to show a progression from “simple” to “complex” functionality and 

to validate the SDR technology aspects of the communication system using a single and most basic 

configuration. The smooth lines on the graph represent the predicted power which are calculated based on 

ISS location and attitude, antenna gimbal angles, TDRS attitude, TDRS pointing angles, antenna gain, 

and RF subsystem losses. The jagged lines are the estimated power using the digital and analog AGC 

values. Although they are not shown on the figure below, power levels for the MGA, 18 kbps SA and MA 

waveforms were similar to the corresponding center frequency at the 72 kbps data rate. In other words, 

the MGA power levels varied per antenna and center frequency, but were very consistent for events with 

the same antenna. Data rate did not affect the receive power level. The SN-LGA forward-link clearly 

provided much lower power to the SDR. This was expected and was due to the fact that the LGA antenna 

is not steerable, has lower gain, and experiences multipath effects. 

Figure 9.—SDR input power. 

-140

-135

-130

-125

-120

-115

-110

-105

-100

0:00 0:07 0:14 0:21 0:28 0:36 0:43 0:50

SDR Input Power (dBm)

Relative Time (hh:mm)

SDR Input Power, Uncoded Waveforms

LGA, MA, 18k

MGA, SA, 72k

MGA, MA, 72k

Actual

Predicted

Actual

Predicted

tual

A
NASA/TM—2014-218316 9 

Receive (Forward-Link) Waveform BER Performance 

The bit error rate (BER) is a key metric used to evaluate the performance of the GD SDR launch 

waveform. Figures 10 to 13 show typical BER curves for each on the four launch waveform tests. The 

BER tester accumulates a running total of received bits and received bit errors. Since the power is 

changing over the entire duration of the event, a total bit error rate over the event is not very meaningful. 

To produce a BER curve, an instantaneous bit error rate was calculated over a 20 sample interval. This 

instantaneous bit error rate data was then plotted against the average estimated Eb/N0, determined from 

the link prediction, over the same 20 sample interval. The BER curves (shown in blue asterisks) in 

Figure 10 to Figure 13 are plotted against the QPSK theoretical curve and ground testing BER data for 

reference. The on-orbit curves are shifted to the left from the ground testing curves. This is because the 

ground data was acquired at ambient temperatures near 25 °C and the on-orbit data was acquired at much 

lower temperatures of 4 to 12 °C. The left shift of about 0.5 dB was expected based upon ground thermal 

vacuum testing performed at similar cold temperatures. 

Figure 11 shows BER data for the only coded waveform tested. Good BER curves are difficult to 

acquire for coded waveforms, because low data rates require very long test times to get an accurate count 

of bit errors. Long tests are not possible given the short event times possible with the TDRSS network. 

Figure 10.—Test 20: BER curve, SN-MGA, SA, 18 kbps, uncoded. 

Ground results at ambient 

temperatures. 

On-orbit results 
NASA/TM—2014-218316 10

Figure 11.—Test 21: BER curve, SN-MGA, MA, 18 kbps, coded. 

Figure 12.—Test 22: BER curve, SN-MGA, SA, 72 kbps, uncoded. 

Ground results at ambient 

temperatures. 

On-orbit results 

Ground results at 

ambient temperatures. 

On-orbit results 
NASA/TM—2014-218316 11

Figure 13.—Test 23: BER curve, SN-MGA, MA, 72 kbps, uncoded. 

TABLE 5.—RETURN-LINK AVERAGE BIT ERROR RATES 

Test Freq. Coherent Forward Rate 

(kbps)

Return Rate

(kbps)

FEC Average BER

Test 20 Event 3 SA No 18 24 No 2.9×10–3

Event 4 SA No 18 24 No 1.3×10–3

Test 21 Event 1 MA No 18 24 No 2.2×10–4

Test 22 Event 3 SA Yes 72 192 No 3.0×10–2

Event 4 SA Yes 72 192 No 3.6×10–2

Test 23 All events MA No 18 24 No N/A (link margin too low)

Transmit (Return-Link) Waveform BER Performance 

Meaningful BER data was difficult to graph for the return-link portion of the launch waveform tests 

because accurate Eb/N0 values were not available. Raw C/N0 values, obtained from NASA White Sands 

Complex (WSC), were used to calculate the Eb/N0. These C/N0 values were not well-understood and 

could vary as much as 3 dB from the real C/N0 value. The variations in the C/N0 appear to be due to noisy 

Eb/N0 measurements and data rate related calculation errors. 

Since accurate Eb/N0 values were not available, meaningful BER curves could not be plotted for the 

return link tests. Instead, the average BER was calculated and shown in Table 5 for a number of return 

link events. The average BER was dependent on the antenna off-pointing profile used for the event. 

Typically the transmitted power varied widely due to off-pointing and resulted in wide variations in 

instantaneous BER. The high Eb/N0 portion of the pointing profile for Tests 20, 21, and 22 achieved zero 

bit errors. 

Ground results at 

ambient temperatures. 

On-orbit results 
NASA/TM—2014-218316 12

Automatic Gain Control 

The GD SDR analog and digital automatic gain control adjusts the received RF power to a constant 

level for receive signal processing. The response of the AGCs to changes in SDR input power and 

temperature is different for each receive-side waveform. The analog AGC varies with center frequency 

(SA/MA) as it is located in the RF module of the radio and operates independently of the radio 

acquisition state. The digital AGC varies with symbol rate (coding and data rate) as it is located in the 

FPGA. Both the analog and digital AGCs vary over temperature, but the analog AGC variation is far 

more significant. The AGCs scale based on total received RF power, so varying noise conditions or the 

presence of interferers will affect the AGC output. 

The on-orbit test events were completed with GD SDR baseplate temperatures ranging typically from 

+4 to +12 °C. Digital and analog AGC data collected during launch waveform characterization testing are 

shown graphically in Figures 14 and 15. The digital AGC plots shown in Figure 14, show that the data 

acquired during on-orbit testing is very similar to the data acquired during ground testing. Notice that the 

digital AGC plots show three distinct trend lines. The trend at a given temperature shows that the digital 

AGC varies with the waveform symbol rate (data rate + coding). The analog AGC plots, shown in 

Figure 15, illustrate that the plots show two distinct trend lines. The analog AGC trend at a given 

temperature is dependent on the center frequency (SA or MA). The plots also show the temperature trend, 

due to the lower temperatures experienced on-orbit. During ground testing the data was obtained at 

ambient temperature and on-orbit data was obtained between 4 to 12 °C. 

Figure 14.—Digital AGC. 

0

50

100

150

200

250

300

-130 -120 -110 -100 -90

Digital AGC

Predicted SDR Input Power (dBm)

Digital AGC

18k, Uncoded, SA,

Test 20 Event 7

18k, Coded, MA, Test

21 Event 5

72k, Uncoded, SA,

Test 22 Event 3

72k, Uncoded, MA,

Test 23 Event 4

18k, Uncoded, SA,

GND at 26°C

18k, Coded, MA, GND

at 26°C

72k, Uncoded, SA,

GND at 26°C

72k, Uncoded, MA,

GND at 26°C
NASA/TM—2014-218316 13

Figure 15.—Analog AGC. 

Acquisition Levels 

One of the goals of the launch waveform characterization tests was to determine the forward-link 

minimum acquisition threshold. This was done by varying the input power to the SDR using antenna offpointing and finding the power level at which the radio reaches state 5 (i.e., acquires the short PN code) or 

when it transitions from state 5 to state 4 (i.e., loses the short code acquisition). State 5 is the minimum 

acquisition level required to receive data. A design requirement for the GD radio was to have a minimum 

acquisition threshold equal to or less than the following 

x –118 dBm for the 18 kbps data rate 

x –112 dBm for the 72 kbps data date 

The acquisition threshold data listed in Table 6 is the total SDR input power at which the SDR can 

acquire the short code and carrier (state 5). The receiver meets the minimum acquisition threshold criteria. 

The acquisition threshold measured during ground testing is included for reference. The ground data was 

acquired at ambient temperatures. The difference between the on-orbit acquisition level and the ground 

acquisition was about 1.5 dB and was consistent across all four test waveforms. The cold (usually 

between 4 and 12° C) on-orbit temperatures results lower the acquisition power level. The lower on-orbit 

radio acquisition levels are due to the improved performance of the radio at lower temperatures from a 

lower noise figure due to lower electronic noise, as well as a lower noise floor in the space environment. 

90

100

110

120

130

140

150

160

-130 -120 -110 -100 -90

Analog AGC

Predicted SDR Input Power (dBm)

Analog AGC

18k, Uncoded, SA,

Test 20 Event 7

18k, Coded, MA,

Test 21 Event 5

72k, Uncoded, SA,

Test 22 Event 3

72k, Uncoded, MA,

Test 23 Event 4

18k, Uncoded, SA,

GND at 26°C

18k, Coded, MA,

GND at 26°C

72k, Uncoded, SA,

GND at 26°C

72k, Coded, MA,

GND at 26°C
NASA/TM—2014-218316 14

TABLE 6.—RADIO ACQUISITION LEVELS 

Test Number Antenna Freq. Forward Rate FEC Radio Acq. Level (dBm) Result

On-Orbit Ground

Test 20 SN-MGA SA 18 k No –125.1 –123.9 Pass

Test 21 SN-MGA MA 18 k Yes –123.7 –122.1 Pass

Test 22 SN-MGA SA 72 k No –119.5 –118.0 Pass

Test 23 SN-MGA MA 72 k No –120.2 –118.5 Pass

Figure 16.—Temperature histograms. 

On-Orbit Temperatures 

The GD SDR has four temperature sensors called GD Temp 1, GD Temp 2, GD PA Temp, and GD 

TCXO Temp. The sensors for GD Temp 1 and GD Temp 2 are located on the outside of the SDR on its 

baseplate. These sensors are connected directly to the Avionics and telemetry is available when the 

Avionics is power on. The other two temperature sensors, GD PA Temp and GD TXCO Temp, are 

located in the Power Amplifier (PA) and the temperature compensated crystal oscillator (TCXO) internal 

to the radio. The telemetry from these temperature sensors is sent from the GD SDR to the Avionics to be 

transmitted to the ground and telemetry is only available when the SDR is powered on. Figure 16 contains 

histograms of all four temperature sensor values over the first year of operation of the GD SDR, showing 

the typical on-orbit temperatures experienced by the SDR. 

Future Work 

Testing of GD SDR launch waveform is complete. Future testing will focus on updating the launch 

waveform to add a forward-link signal-to-noise ratio (SNR) estimator. 

Conclusions 

This report shows the on-orbit performance of the GD SDR. Every test was completed at least twice 

in order to verify repeatability of results. The on-orbit test results obtained during the launch waveform 

characterizations test were compared to results from ground testing of the flight model SDR. The on-orbit 

results were found to be very similar to the ground results, so the ground testing was determined to be a 

good predictor of on-orbit performance. All tested waveform configurations met or exceeded the expected 

BER performance, the SDR signal acquisition levels met the minimum acquisition criteria, the SDR input 

power was close to the predicted power, and the analog and digital AGC levels were as expected. 
NASA/TM—2014-218316 15

Appendix A.—GD Test Matrix 

TABLE 7.—LAUNCH WAVEFORM TEST MATRIX 

Test ID Test 20: SA noncoherent, full duplex, 

uncoded, 18/24

Test 21: MA noncoherent, full duplex, 

coded, SpW, 18/24

Test 22: SA noncoherent, full-duplex, 

72/192

Test 23: MA noncoherent, full-duplex, 

SpW, 72/192

SDR GD GD GD GD

SCAN Testbed Antenna SN-MGA SN-MGA SN-MGA SN-MGA

RF Subsystem Path Path 2 

(S1=2,S2=1,S3=1)

Path 2 

(S1=2,S2=1,S3=1)

Path 2 

(S1=2,S2=1,S3=1)

Path 2 

(S1=2,S2=1,S3=1)

Waveform ID 

(Forward/Return)

182/218 183/221 206/242 208/246

Data Group DG1 DG1 DG1 DG1

Mode M2 M2 M2 M2

Coherency Non-coherent Non-coherent Non-coherent Non-coherent

Forward(Rx) Carrier 

Frequency

S SA FL 

(2.041 GHz)

S MA FL 

(2.106 GHz)

S SA FL 

(2.041 GHz)

S MA FL 

(2.106 GHz)

Return(Tx) Carrier 

Frequency

S SA FL 

(2.2165 GHz)

S MA FL 

(2.2875 GHz)

S SA FL 

(2.2165 GHz)

S MA FL 

(2.2875 GHz)

RF Operation @ Spacecraft Duplex @ TDRS Duplex @ TDRS Duplex @ TDRS Duplex @ TDRS

Forward(Rx) Data Rate 

(kbps)

18 kbps 18 kbps 72 kbps 72 kbps

Return(Tx) Data Rate (kbps) 24 kbps 24 kbps 192 kbps 192 kbps

Spacewire Mode 

(BER/Logging/None)

None BER None BER

APS Mode Open Loop Open Loop Open Loop Open Loop

Special APS Config? Embedded TRK 

errors

Embedded TRK 

errors

Embedded TRK errors Embedded TRK errors

APS Logging, Period 100 ms 100 ms 100 ms 100 ms

Number of Passes 2 2 2 2

Desired Link Performance SDR input power: 

–125 to –116 dBm

SDR input power: 

–122 to –118 dBm

SDR input power: 

–119 to –110 dBm

SDR input power: 

–119 to –110 dBm

Link Path (TDRS/GN) F9-F10 F10 F9-F10 F10

TDRS Antenna (SA1/SA2) Either 

(but documented)

SA3 / Any Either 

(but documented)

SA3 / Any

TDRS Mode (S {N/H 

Power},Ka {P/A Track})

S - Normal Power N/A S - Normal Power N/A

Tracking (Range/1WDoppler/2W-Doppler)1W Doppler 1W Doppler 1W Doppler 1W Doppler

White Sands SGLT Used Any

(but documented)

Any 

(but documented)

Any (but documented) Any (but documented)

Link Pass Start Time No Earlier than 11:30 

GMT

No Earlier than 11:30 

GMT

No Earlier than 11:30 

GMT

No Earlier than 11:30 

GMT

Link Pass Stop Time No Later than 18:30 

GMT

No Later than 18:30 

GMT

No Later than 18:30 

GMT

No Later than 18:30 

GMT

Ground System Config 

(EFEP/SFEP)

Yes Yes Yes Yes

Onboard File storage ~10 Mb ~10 Mb ~10 Mb ~10 Mb

ISS S- & Ku-Band Overlap 

Coverage?

Yes Yes Yes Yes

Without Obscuration? Yes Yes Yes Yes

ISS BAD (TimestampedPosition, Attitude, Beta 

Angle, Altitude) Requested

Yes (TimestampedPosition,Attitude)Yes (TimestampedPosition,Attitude)Yes (TimestampedPosition,Attitude)Yes (TimestampedPosition,Attitude)
NASA/TM—2014-218316 16

Test ID Test 20: SA noncoherent, full duplex, 

uncoded, 18/24

Test 21: MA noncoherent, full duplex, 

coded, SpW, 18/24

Test 22: SA noncoherent, full-duplex, 

72/192

Test 23: MA noncoherent, full-duplex, 

SpW, 72/192

Test Measurement at Ground 

Requested

No No No No

SNAS Data Requested SN Delog, UPD UPD SN Delog, UPD UPD

TDRS/GN Measured EIRP 

Requested

Yes Yes Yes Yes

Additional Notes In order to do 

acquisition threshold 

test, starting power 

must be less than -

125 dBm; no need to 

wait until forward 

acquisition to 

transmit

In order to do 

acquisition threshold 

test, starting power 

must be less than -

122 dBm; no need to 

wait until forward 

acquisition to 

transmit

May need change 

TDRS power or STB 

antenna to achieve 

desired SDR input 

power range; In order 

to do acquisition 

threshold test, starting 

power must be less 

than -119 dBm; no 

need to wait until 

forward acquisition to 

transmit

May need change 

TDRS power or STB 

antenna to achieve 

desired SDR input 

power range; In order 

to do acquisition 

threshold test, starting 

power must be less 

than -119 dBm; no 

need to wait until 

forward acquisition to 

transmit

Success Criteria Verify acquisition 

threshold; verify 

BER curves; verify 

AGC levels

Verify acquisition 

threshold; verify 

viterbi threshold; 

verify AGC levels

Verify acquisition 

threshold; verify BER 

curves; verify AGC 

levels

Verify acquisition 

threshold; verify BER

curves; verify AGC 

levels