# Presentation: 301256

## Section 20

_***Section 20***_
***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

## Verification Matrix

## Accumulated Power On Time for EO-1 S/C & Components

## 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)*

## RF Communications

***RF Communications***

***Test Results***
***All Data Processed Looks Good***
***Significant Non-Conformance and Critical PRs***
***S-Band:  EO1-WOA-674 and EO1-WOA-738***
*Incorrect Modulation Index for Different Data Rates*
***X-Band:  EO1-WOA-681 and EO1-WOA-676***
*X-Band Failure Detection and Correction Limits Faulting*
***X-Band:  Frequency Shift Anomaly***
*See X-Band RF Exciter Frequency Shift Special Topic*

## RF Communications

***RF Communications***

***Configuration Changes and Corrective Actions***
***S-Band:  Update COM RSN Software to Use Proper GN Voltage Levels for 2 Kbps, 32 Kbps, 1 Mbps, and 2 Mbps.  Completed 11/99.***
***X-Band:  Update X-Band RSN Software to Fix Failure Detection and Correction Limits and Handling.  Completed 11/99.***
***X-Band:  Change X-Band Attenuator to 2 dB.  Completed 11/99.***
***Replace All S-Band and X-Band RF GSE Cables.  Completed 1/00.***

## RF Communications

***RF Communications***

***Action Item and Problem Report Status***
***All Action Items closed***
***All Problem Reports closed***
***Statement of Readiness & Residual Risks***
***RF Communications Subsystem is ready to ship pending ...***
*Reinstallation and testing of WARP*
*Additional X-band Regression Testing*
*Review of Final CTV Report*
***X-Band Frequency Shift Anomaly remains a minor residual risk***

## Special Topic:

***X-Band RF Exciter Frequency Shift***

*** ******. . . Nicholas Speciale***
*EO-1 Mission Technologist*

## EO-1 Flight Data System Architecture

## EO-1 WARP Hardware Architecture

**Memory Interface**
**Board**

**1773**
**Data Bus**
**RT #1**

**Data   1 Gbps**

**Memory Board**
**24 Gbits**

**Data  1 Gbps**

**RF**
**Exciter**

**Data  250  Mbps**

**Parallel**
**RS-422**
**500 Mbps**

**LVPC/**
**RSN**

**S-Band**
**Data**
**2 Mbps**

**1773**
**Data Bus**
**RT #2**

**+28V**
**Power**

**Modulated**
**X-Band**
**105 Mbps**

**Memory Board**
**24 Gbits**

**Processor**
**Board**

- 52.5Mbps I chan

- 52.5Mbps Q chan

## X-Band Frequency Shift Anomaly

***X-Band Frequency Shift Anomaly***

***After S/C level vibration on 8/4/99, the first attempt to turn on WARP X-band downlink resulted in inability to achieve carrier lock (with fill data on) on 8225.0Mhz signal.  Situation stayed this way for approx. 24hrs.***
***Test personnel diagnosing situation observed apparent frequency shift approximately 6-7Mhz of entire spectrum (QPSK spectrum as expected but frequency shifted);  however detailed analyzer printouts were not obtained.  XPAA was vindicated as problem persisted  when cables were output directly from RF Exciter.***
***The next day as personnel brought in additional test equipment to try and diagnose situation further, the problem disappeared and WARP/RF Exciter/XPAA worked nominally (to this date).  During the subsequent troubleshooting, some S/C bay doors were opened, closed and manipulation of GSE and WARP cables occurred.***
***Problem has not manifested itself since that date through over 300 downlink testing cycles of WARP, RF Exciter and XPAA, about half of which occurred in TB/TV.  This problem never manifested itself in WARP box level testing either (about 300 D/L cycles).***

## Initial X-Band Anomaly

***Initial X-Band Anomaly***

***Detailed fault analysis of all WARP/RF Exciter elements conducted in late August/early Sept, no theory proven conclusively. Report on anomaly was generated and distributed.***
***Most likely suspect at that time attributed to intermittent (loosened during spacecraft vibration)  external cable between WARP MIC and RF Exciter Cards, however, intercable harness inspection, resistance measurement of cabling was performed and all looked nominal.***

## Initial X-Band Anomaly Investigation Recommendations

***Initial X-Band Anomaly Investigation Recommendations***

***1>******	******Freeze state of S/C (WARP) and record on GSE measured spectrum if problem reoccurs -   additional printers and procedures in place to record all X-band downlink RF and baseband characteristics.***
***2>******	******Visually inspect and test resistance of WARP MIC to RF Exciter clock and data harness- visual and resistance measurement made on 9/6 but all measurements were nominal.***
***3>******	******Recharacterize RF-Exciter spectrum against  WARP I&T results to see if any changes occurred - test performed in mid Sept but showed no differences***
***4>******	******Take additional X-band downlinks during TB/TV to make problem reoccur - Over 150 X-band downlinks performed, no reoccurrence of problem.***
***5>******	******Insert WARP - X-band baseband GSE into test port of MIC in case problem reoccurs - performed, will allow for viewing of MIC baseband output should problem reoccur.***
***6>******	******Complete flight qualification of second MIC and RF Exciter modules in case of failure of current modules - completed in late October.***
***7>******	******Deintegrate WARP from S/C and visually inspect all interharness between MIC and RF Exciter, measure impedances between these cards.***
***8>******	******Recommend that problem be further examined by an independent team of experts. ***

## AETD Investigation Team

***AETD Investigation Team***

***Formed on 12/1/99, consists of***
***Bob Kichak, Code 560, Chairman***
***John Sutton, Code 564***
***George Winkert, Code 564***
***Dave Israel, Code 567***
***Beverly Settles, Code 561***
***Sheng Cheng , APL***
***Charter: ***
*** “******To look at the WARP RF frequency issue from the point of view of trying to disprove the proposed conclusion that we should fly as is given that we have been unable to make it "break" again, and we have an operational work-around anyway. They should come at this by assuming that something is wrong with the design, and that the problem that we observed is an indication of that flaw.”***

## AETD Team Findings

***AETD Team Findings***

***1)******	******Most likely cause of anomaly on August 4th was kinked or problem RF GSE cables between the X-band RF GSE rack and the S/C X-band interfaces***
***Kinks can cause Selective Frequency Attenuation (SFA)***
***SFA can cause data errors and/or loss of carrier lock with spectrum distortion which may be interpreted to be a shift***
***2)******	******Flight hardware causes (RF Exciter or WARP/MIC) causes have been all but ruled out***
***Continuity,grounding and visual inspection all look nominal***
***Re-environmental testing of WARP with additional residual carrier monitoring should collaborate findings***
***3)******	******Team Report update will be available in late April***

## WARP Frequency Shift Summary

**S/C**
**Config.**
**& Test**

**Phased**
**Array**
**Antenna**

**Flight**
**Cables &**
**Inter-**
**connects**

**LVPS**

**Data**
**Pattern**

**MIC**

**RF Exciter**

**EGSE**
**Test**
**Config.**

**EGSE**
**Cables**

**Checked**
**and all**
**normal**

**Problem**
**continued**
**when RF**
**output **
**taken**
**from RF**
**Exciter**
**rather**
**than**
**antenna**
**hat coupler**

**Inspected **
**and**
**found to **
**be okay**

**Voltages**
** ****read at **
**BOB during**
**anomaly **
**and found **
**to be okay; **
**wire**
**continuity **
**& grounding **
**verified by**
**measurement**
**TLM okay**

**Appears**
**remote --**
**Not aware **
**of a **
**specific**
**pattern **
**that could **
**cause**
**anomaly;**
**analyzer**
**setting **
**may**
**be a factor**

**Stuck-at **
**Bit**
**produces**
**significant**
**spectrum**
**distortion;**
**Data **
**pattern**
**issue due **
**to**
**malfunction**
**remote**
**possibility**

**TCXO**
**frequency **
**shift**
**and return **
**to normal**
**unlikely;**
**visual**
**inspection **
**ok; internal**
** ****wiring and **
**grounding **
**verified; **
**card >30**
**temp cyc **

**Appears**
**remote --**
**Attenuator**
**settings in**
**EGSE**
**somewhat**
**complex to**
**configure**

**RF cable**
**replaced **
**after TV **
**test due to **
**data quality**
**problems;**
**cable**
**measured**
**and found **
**bad; **
**visible **
**signs of **
**cable **
**damage**

**Legend:   **

**Ruled out**

**Highly unlikely**

**Most likely**

***WARP Frequency Shift Summary***
**EO-1 Spacecraft completed 3 axis random vibration; WARP powered off during test (normal launch mode)**
**Spacecraft moved back from vibration test cell to clean tent and connected to EGSE**
**Initial power on of WARP showed failure to achieve carrier lock in RF rack**
**Initial troubleshooting with spectrum analyzer and frequency counter indicated an apparent 6 MHz frequency increase while modulation applied; normal carrier frequency when modulation signal off**
**RF signal takeoff moved from antenna hat coupler to RF Exciter output and problem persisted**
**Voltages to RF Exciter measured and found to be nominal with BOB**
**Spacecraft powered off over night; bay doors opened for further troubleshooting**
**Upon next power up, all normal**
**Problem has not recurred since, including during thermal-vacuum testing of S/C and subsequent testing**

## Frequency Shift Anomaly Summary

***Frequency Shift Anomaly Summary***

***Fact that anomaly self-healed and has not been able to be re-induced makes an absolute determination of the root cause impossible***
***Lack of documented data (e.g. spectrum photos, etc.) during initial troubleshooting significantly hampers investigation***
***Design was evaluated, and no specific design issues were identified that could cause the anomaly***
***RF Exciter was visually inspected following the anomaly and wiring resistance measurements were made.***
***Workmanship looked very good and all wiring measurements were normal.***
***MIC cables were inspected and found to be okay***

## Frequency Shift Anomaly Summary

***Frequency Shift Anomaly Summary***
*(continued)*

***The subsequent power supply anomaly could not have caused the frequency shift -- power supply anomaly resulted in shutdown of LVPC outputs and would have been detected.  LVPC TLM nominal during frequency shift anomaly. ***
***The most likely cause of the anomaly is Selective Frequency Attenuation (SFA) due to a faulty/damaged external RF EGSE cable producing an apparent frequency shift as observed at the RF Rack spectrum analyzer.***
***RF Cables show significant visual and electrical damage***
***RF Cables had to be replaced after the anomaly due to data quality problems***
***Demonstrated possibility of an apparent frequency shift at spectrum analyzer due to cable reflections***

## Other, much less likely causes include an actual frequency shift of the TCXO with modulation on and return to normal carrier frequency with modulation off or a data pattern other than a “stuck at” bit that might cause an apparent frequency shift
Residual carrier was measured after the anomaly and frequency closely matched initial card test data
To mitigate the risk of any other, more subtle potential cause due to workmanship or parts defects, retest of the WARP will include thermal-vacuum or cycling  testing with one unpowered temperature cycle to survival limits and 3 cycles to qualification temperature limits, conducted susceptibility and emissions tests, and unpowered vibration to qualification limits
The RF Exciter residual carrier frequency will be monitored throughout all powered testing to verify stability, including prior to and following vibration test

***Other, much less likely causes include an actual frequency shift of the TCXO with modulation on and return to normal carrier frequency with modulation off or a data pattern other than a “stuck at” bit that might cause an apparent frequency shift***
***Residual carrier was measured after the anomaly and frequency closely matched initial card test data***
***To mitigate the risk of any other, more subtle potential cause due to workmanship or parts defects, retest of the WARP will include thermal-vacuum or cycling  testing with one unpowered temperature cycle to survival limits and 3 cycles to qualification temperature limits, conducted susceptibility and emissions tests, and unpowered vibration to qualification limits***
***The RF Exciter residual carrier frequency will be monitored throughout all powered testing to verify stability, including prior to and following vibration test***

***Frequency Shift Anomaly Summary***
*(continued)*

## RF Exciter Fault Tree Analysis(Page 1 of 2)

## RF ExciterFault Tree Analysis(Page 2 of 2)

## Tests & Other Collaborating Evidence

***Tests & Other Collaborating Evidence***

***1)******	******Dave Israel’s multipath demonstration***
***software demonstration***
***hardware demonstration using simulated multipath ***
***reflectometer measurement of problem GSE cable ***
***2)******	******Characterization of X-band RF GSE cables   ***
***significant distortion and kinking found***
***3)******	******Problems with X-band compatibility testing***
***performed in Sept, found significant X-band link performance problems***
***used same suspect GSE cables ***
***4)******	******Further problems with I&T testing before replacement of cables***
***eventually replaced all cables and had nominal performance since Nov***
***5)******	******Grounding and inspection of RF Exciter showed nominal results***

## Hardware Multipath Simulation Spectrum

- Reflected signal level -5.4 dB

## TDR Test Result - The Whole “RF3” Cable

***TDR Test Result - The Whole “RF3” Cable***

## TDR Test Result - “RF3” Cable with Induced -5.4 dB Reflection

- 20log(-1.324/-2.459) = -5.4 dB

***TDR Test Result - “RF3” Cable with Induced -5.4 dB Reflection***

## Frequency Performance of Cable “RF3”

## E0-1 Spectrum (Test Modulator) Through “RF3” Cable

## Frequency Performance of Cable “RF1 #34”

## Frequency Performance of Cable “#34”

## Frequency Performance of Cable “RF2 (#35)”

## Frequency Performance of Cable “#35”

## Frequency Performance of New Gore Cable

- Note:  This is not an EO-1 cable.  This is a short Gore cable tested for reference purposes only.

## X-Band RF Exciter Anomaly Impact on Mission

***X-Band RF Exciter Anomaly Impact on Mission***

***Significant impact to mission would occur if anomaly occurs and cannot be resolved by ground stations changes***
***Ability to downlink only a single DCE per day assuming increased S-band contingency data and ground station passes***
*10 passes x  (12 min x 60 sec x 2x10e6 b/sec ) = 14 Gbits/day  = 1 DCE*
*This is approx. 1/4 of anticipated image data return  (baseline:4 DCE’s per day via X-band)*
***Inability to fully validate X-band Phased Array Antenna***
*Could perform carrier only or RF tests only*
*BER and noise characterization would be extremely difficult to validate*
***Could still support Minimal Mission success through S-band. ***

## Summary

***Summary***

***Most likely cause of X-band Frequency Shift Anomaly on August 8th was problem GSE cables between S/C and X-band GSE***
***Supported by multipath simulations and cable testing conducted during January***
***Inspections and testing on RF Exciter and MIC cards***
***Fault tree and testing immediately after anomaly indicates any other potential causes to be much more remote***
***Full re-characterization X-band spectrum planned during WARP re-qualification***
***Residual risk to EO-1 Minimal Mission is small ***
***S-band backup serves to preserve Minimal Mission capabilities***

## Special Topic:

***Frequency Conflicts with Landsat 7***

*** ******. . . Dan Mandl***
*EO-1 Operations Manager*

## Frequency Conflicts with Landsat 7

***Frequency Conflicts with Landsat 7***

***EO-1 and Landsat 7 both use the X-band to downlink images***
***They do not use the same ground stations***
***EO-1 ground stations:***
***Primary:  Alaska***
***Secondary:  Norway, Wallops***
***Landsat 7 ground stations:***
***Primary:  Sioux Falls***
***Secondary:  Alaska, Norway***
***Both use S-band for telemetry***
***Both use S-band uplink for command & control***

## EO-1 & Landsat 7 Frequencies

***Shared use of X-band at 8215 MHz is recommended***

## Special Topic:

***Demonstration of S-Band Back-Up***

*** ******. . . Nick Speciale  ***
*EO-1 Mission Technologist*

## EO-1 WARP Hardware Architecture

**Memory Interface**
**Board**

**1773**
**Data Bus**
**RT #1**

**Data   1 Gbps**

**Memory Board**
**24 Gbits**

**Data  1 Gbps**

**RF**
**Exciter**

**Data  250  Mbps**

**Parallel**
**RS-422**
**500 Mbps**

**LVPC/**
**RSN**

**S-Band**
**Data**
**2 Mbps**

**1773**
**Data Bus**
**RT #2**

**+28V**
**Power**

**Modulated**
**X-Band**
**105 Mbps**

**Memory Board**
**24 Gbits**

**Processor**
**Board**

- 52.5Mbps I chan

- 52.5Mbps Q chan

- S-band Contingency data

## S-Band Contingency Backup Testing

***S-Band Contingency Backup Testing***

***Exercised during WARP I&T and S/C testing***
***WARP Testing - verified over 50 times***
***S/C Testing - exercised over 20 times during I&T since July***
***Spacecraft Testing -verified interface approximately 20 times***
***Verified during each functional test (run 8 times)***
***Verified during each WARP integration ( run 3 times)***
***Verified during each CPT (CPT’s 7,8 and 11) (9 times)***
***Tested end-to-end (through L0 and instrument level 1 processing)  - 6 times and through Instrument turn on Simulation in November 99’***
***Will be used operationally for quick look data during instrument turn-on’s and first time instrument and WARP events to validate data record/playback from WARP ***
***Will be exercised 6-8 times during first ten days of on-orbit operations.***