# Presentation: 526083

## Section 21

_***Section 21***_
***Communications***

*** ******. . . Deane Charlson***
*EO-1 RF Engineer*

## RF Communications

***RF Communications***

***Overview of S-Band Design***
***Basic SMEX Architecture and Performance***
*TDRS S-Band 2 Kbps Single Access Forward and Return*
*GN S-Band 2 Kbps Uplink*
*GN S-Band 2 Kbps, 32 Kbps, 1 Mbps, and 2 Mbps Downlinks*

## RF Communications

***Overview of X-Band Design***
***105 Mbps QPSK Downlink Similar to RadarSat***

- WARP

- Exciter/
- Modulator

- Coax Cables
- X-band Signal Modulated with Data

- ESN Control Interface / Processor

- Science Data

- Pointing Commands from Spacecraft
- via 1773 interface

- Phase Settings

**XPAA**

- X-band Signal Radiated to Ground

- 2 dB Attenuator

- x 64

## “As Run” Verification Matrix

## Projected Power On Time

## RF Communications

***RF Communications***

***Verification and Testing Approach***
***Acceptance Test Data Package (L3, Boeing, Gore, Litton)***
***Subsystem and System Level Testing (WOA Numbers)***
*Integration and Test (171, 277, 282, 296, 476, 494)*
*Functional Tests (460, 607, 692, 897)*
*Compatibility Testing with CTV for GN and TDRSS (410, 590, 693)*
*Regression Testing after FSW RSN Updates (493, 495, 510, 511, 667, 719, 766, 913)*
*Calibration of AGC Curves (895)*
*Specific Work Orders to Investigate Issues (559, 665, 734, 848, 870, 887, 899)*
***Extensive RF Functional Testing during T/V II***

## RF Communications

***RF Communications***

***Test Results***
***Anomaly in S-Band Transponder During TVAC #2***
***Significant Non-Conformance and Critical PRs***
***S-Band:  EO1-WOA-1095, 1099, and 1100***
*Automatic Gain Control (AGC) Telemetry Showed Dropouts/Storms*
*Covered in Special Topic to follow*
***X-Band:  EO1-WOA-1099***
*X-Band Phased Array Experienced -19 degrees C*
*Covered in XPAA presentation*

## RF Communications

***RF Communications***

***Action Item and Problem Report Status***
***All Action Items Closed Except for S-Band Transponder***
***All Problem Reports Closed Except for S-Band Transponder***
***Statement of Readiness & Residual Risks***
***RF Communications Subsystem is ready to ship pending ...***
*Completion of S-Band Anomaly Investigation and Repair*
*Review of Final CTV Report*
***X-Band Frequency Shift Anomaly remains a minor residual risk and is a Redbook candidate.***

## Special Topic:

***Compatibility Test Van (CTV) Results***

*** ******. . . Bill Jupin***
*RF Engineer *

## CTV Data QualityBackground

***CTV Data Quality****Background*

***Data Quality Test involves plotting data errors as a function of Eb/No, (signal / noise ratio per Hz per bit).***
***Data Quality curves indicate overall system loss factor,which is difference between actual and theoretical Eb/No curves.***
***Presence of Reed - Solomon EDAC on data packets means that frame errors are not a good measure of performance at lower error rates.***
***Only end-to-end system as a whole can be measured, individual component loss contributions cannot be isolated or determined.***

## CTV Data QualityHistory

***CTV Data Quality****History*

***Data Quality test run on EO1 system in July 1999 timeframe indicated poor data quality, or unusually high system loss factor.***
***EO1 system test preceded infamous X-Band Exciter frequency anomaly by approximately one month.***
***Data Quality Tests run previously at Litton on Exciter / GSE combination indicated system loss of 2.5 dB warmed up @ 1e-6 BER, which is excellent performance (0.5 dB greater than typical GSE performance spec).***
***Assumption has been that poor test results are manifestations of hat coupler/bad cable interactions.  (Exciter frequency anomaly attributed to bad test cable.)***

## New test run on July 3 - 4 as part of the T/V II activities
Test repeated at plateaus of 40 degrees C and -10 degrees C.
Controlled conditions allowed varying signal/noise ratio in 0.5 dB increments.
Calibration of test setup done using super high quality spectrum analyzer.

***New test run on July 3 - 4 as part of the T/V II activities***
***Test repeated at plateaus of 40 degrees C and -10 degrees C.***
***Controlled conditions allowed varying signal/noise ratio in 0.5 dB increments.***
***Calibration of test setup done using super high quality spectrum analyzer.***

***CTV Data Quality****Test Scenario*

***CTV Data Quality****Current Test Results*

## Current test results indicate system is performing as designed (4.22 dB average system loss factor).
Additional 1.72 dB (4.22 dB -2.5 dB) system loss factor is attributed to intersymbol interference effect of hat coupler.
Hat coupler effect had been observed previously during initial XPAA / Exciter integration and test.
Spectrum of exciter/XPAA combination is clean, well below NTIA specs within 400 MHz bandwidth.

***Current test results indicate system is performing as designed (4.22 dB average system loss factor).***
***Additional 1.72 dB (4.22 dB -2.5 dB) system loss factor is attributed to intersymbol interference effect of hat coupler.***
***Hat coupler effect had been observed previously during initial XPAA / Exciter integration and test.***
***Spectrum of exciter/XPAA combination is clean, well below NTIA specs within 400 MHz bandwidth.***

***CTV Data Quality****Summary / Wrap Up*

## Special Topic

***S-Band Transponder AGC Anomaly***

*** ******. . . Deane Charlson***
*EO-1 Communications Lead*

## S-Band Transponder AGC AnomalyBackground

***S-Band Transponder AGC Anomaly****Background*

***AGC telemetry is an analog signal digitized by COMM RSN to 10 bit accuracy. Provides a measure of signal strength when receiver is in LOCK.***
***Dependent on both temperature and modulation. Requires significant calibration / characterization to obtain accurate RF input level telemetry data. ***
***Once characterized, provides good visibility into the operating mode of receiver, as well as the command uplink link margin.***

## First occurrence was during TVAC #1
Isolated instances of higher than normal AGC noise. 
Three PR’s generated on isolated command dropouts. PR’s were later closed when problem could not be repeated.
No correlation was made at the time between command dropouts and AGC noise events.
Events were attributed to Hyperion cyro-cooler generating transient noise. Noise spikes have also been known to occur randomly in a thermal vacuum environment.
AGC / command dropout anomaly never occurred at ambient temperature or pressure conditions during time between thermal vacuum testing
Extensive AGC calibration tests did not reveal abnormal noise levels or receiver LOCK characteristics

***First occurrence was during TVAC #1***
***Isolated instances of higher than normal AGC noise. ***
***Three PR’s generated on isolated command dropouts. PR’s were later closed when problem could not be repeated.***
***No correlation was made at the time between command dropouts and AGC noise events.***
***Events were attributed to Hyperion cyro-cooler generating transient noise. Noise spikes have also been known to occur randomly in a thermal vacuum environment.***
***AGC / command dropout anomaly never occurred at ambient temperature or pressure conditions during time between thermal vacuum testing***
***Extensive AGC calibration tests did not reveal abnormal noise levels or receiver LOCK characteristics***

***S-Band Transponder AGC Anomaly****History of Problem*

## During thermal vacuum testing, problem only appeared after 20 hours of vacuum.
Problem was intermittent --- approximately once every few hours, without obvious correlation to spacecraft or external events.
Problem reappeared during TVAC #2 after several days of cycles.
Problem occurred with severe AGC noise and command dropouts at low temperature plateau.
Investigation was started. Investigative steps are listed below.
Fault tree was constructed, with likely failure seen to be transponder.
Fault isolation process initiated while S/C was still in chamber.

***During thermal vacuum testing, problem only appeared after 20 hours of vacuum.***
***Problem was intermittent --- approximately once every few hours, without obvious correlation to spacecraft or external events.***
***Problem reappeared during TVAC #2 after several days of cycles.***
***Problem occurred with severe AGC noise and command dropouts at low temperature plateau.***
***Investigation was started. Investigative steps are listed below.***
***Fault tree was constructed, with likely failure seen to be transponder.***
***Fault isolation process initiated while S/C was still in chamber.***

***S-Band Transponder AGC Anomaly****History of Problem*

## EO-1 Transponder Anomaly Fault Tree

## Swapped cables to eliminate intermittent cable with bad VSWR. No effect seen.
Installed spectrum analyzer on ZENITH port. Internal hybrid provides isolation from NADIR port and ability to see noise generated internal to chamber. No noise observed during anomaly.
GSE and cable setup completely revised. GSE re-located close to chamber. Anomaly persisted.
TSS2000 uplink modulator in GSE rack swapped out with external HP generator. No effect seen on anomaly.
Subcarrier modulator signal examined for irregularities, none seen.

***Swapped cables to eliminate intermittent cable with bad VSWR. No effect seen.***
***Installed spectrum analyzer on ZENITH port. Internal hybrid provides isolation from NADIR port and ability to see noise generated internal to chamber. No noise observed during anomaly.***
***GSE and cable setup completely revised. GSE re-located close to chamber. Anomaly persisted.***
***TSS2000 uplink modulator in GSE rack swapped out with external HP generator. No effect seen on anomaly.***
***Subcarrier modulator signal examined for irregularities, none seen.***

***S-Band Transponder AGC Anomaly****Fault Isolation Steps*

## Playbacks of data during events confirmed that anomalies occurred at specific points in time relative to turning ON and OFF of transmitter while at plateaus.
Using transmitter as heat source, AGC events were reproduced regularly, thus establishing the temperature gradient nature of the problem.
During multiple recreations of event, it was observed that downlink errors also occur when the transponder is in COHERENT mode, but not in NON-COHERENT mode. This strongly pointed to a transponder problem, and not an internal cable or hat coupler problem.
GSE and cables were returned to nominal configuration. Additional CTV cable was installed to allow CTV command of the spacecraft directly, eliminating GSE.

***Playbacks of data during events confirmed that anomalies occurred at specific points in time relative to turning ON and OFF of transmitter while at plateaus.***
***Using transmitter as heat source, AGC events were reproduced regularly, thus establishing the temperature gradient nature of the problem.***
***During multiple recreations of event, it was observed that downlink errors also occur when the transponder is in COHERENT mode, but not in NON-COHERENT mode. This strongly pointed to a transponder problem, and not an internal cable or hat coupler problem.***
***GSE and cables were returned to nominal configuration. Additional CTV cable was installed to allow CTV command of the spacecraft directly, eliminating GSE.***

***S-Band Transponder AGC Anomaly****Fault Isolation Steps*

## CTV commands spacecraft and problem was also reproduced by turning transmitter ON and OFF during hot soak. At this point all external cables and GSE were removed from fault consideration.
Problem was repeated, this time with all non-essential spacecraft systems un-powered, and using external supply power.
After returning to ambient temperature and pressure, test cable was installed on skin connector of spacecraft (bypasses hat couplers and hybrid).
Testing was repeated, first at ambient pressure, and then at vacuum with transmitter cycles, but problem did not occur after 8 hours of tests, using either normal antenna port or skin connector port.
T/V tests are concluded, and transponder was removed.

***CTV commands spacecraft and problem was also reproduced by turning transmitter ON and OFF during hot soak. At this point all external cables and GSE were removed from fault consideration.***
***Problem was repeated, this time with all non-essential spacecraft systems un-powered, and using external supply power.***
***After returning to ambient temperature and pressure, test cable was installed on skin connector of spacecraft (bypasses hat couplers and hybrid).***
***Testing was repeated, first at ambient pressure, and then at vacuum with transmitter cycles, but problem did not occur after 8 hours of tests, using either normal antenna port or skin connector port.***
***T/V tests are concluded, and transponder was removed.***

***S-Band Transponder AGC Anomaly****Fault Isolation Steps*

## S-Band Transponder AGC Anomaly

***S-Band Transponder AGC Anomaly***

***After thermal vacuum was completed, transponder was removed and returned to LORAL.***
***LORAL succeeded in recreating problem. ***
***Fault diagnosis is continuing, with emphasis on a VCXO subassembly in the receiver.***
***Based on results of diagnosis, LORAL will propose a rework plan, which will include:***
*Complete functional test*
*3 axis vibration – launch levels*
*Box level thermal vacuum --- 8 cycles*
***Assuming no problems, the transponder will be returned and reintegrated at VAFB NLT Sept. 9.***

## Recommended TransponderRe-Integration Steps

***Recommended Transponder******Re-Integration Steps***

***All RF links at site should be pre-tested and characterized before transponder arrives.***
***Safe to mate procedures to ensure the integrity of transponder interfaces are well established.***
***Fully utilize RF functional tests to re-characterize transponder, compare with as-run data from prior thermal vacuum***
***Conduct CTV testing***

## EO-1 Launch Site S-Band Integration

***S-Band Integration***

****16***

****20***

****32***

****72***

****184***

****188***

****196***

**** Denotes cumulative hours on S-band following integration***

## EO-1 Launch Site Flow

****208***