# Presentation: 301259

## Section 14

_***Section 14***_
***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 Return Link Only*
*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

## RF Communications

***RF Communications***

***Verification and Testing Approach***
***Acceptance Test Data Package 9/96***
***Subsystem Level Testing Since 8/99***
*Comprehensive Performance Tests*
*EMI/EMC Testing*
*Thermal Vacuum Testing*
*Functional Testing*
*Specific Work Orders to Investigate Issues*
***Test Results***
***All Data Processed Since August Looks Good Except for a Single Non-Conformance Issue***

## RF Communications

***RF Communications***

***Significant Non-Conformance and Corrective Actions***
***GN Amplitude Drive Voltage***
*Need a Higher Voltage Level Than 3.3 Volts From COM RSN To Establish BPSK for 2 Mbps Downlink*
*COM RSN Hardware Change Would Be Required*
*Impacts Ground Station Receivers*
***Configuration Changes***
***Update COM RSN Software to Use Proper GN Voltage Levels for 2 Kbps, 32 Kbps, and 1 Mbps.  Completed 11/99.***
***Update X-Band RSN Software to Fix Failure Detection and Correction Limits and Handling.  Completed 11/99.***

## RF Communications

***RF Communications***

***Action Item Status***
***EO1-WOA-681 Thermal Vacuum Testing - Transition to Cold***
*Event# 20 PR# 18.  During TDRS/CTV Testing Receiver and Detector Showed Lock While Receiver AGC was -244.39 dBm.*
***EO1-WOA-682 Thermal Vacuum Testing - Transition to Hot***
*Event# 20 PR# 8.  Command Dropout and Fluctuating AGC.  Problem Believed to be External to Spacecraft.*
***EO1-WOA-770 EMI/EMC Testing In Clean Tent***
*Event# 20 PR# 1.  Lost Command Uplink on S-Band While Changing Spectrum Analyzer Settings.  Believed to be Internal Problem With RF Rack.*
***Statement of Readiness & Residual Risks***
***RF Communications Subsystem is Ready to Ship Pending Review of Final CTV Test Report and Ground Station Receiver Investigation.***

## Special Topic:

***Special Topic:***
***RF Frequency Shift Anomaly***

*** ******. . . 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 Anomaly

***X-Band Anomaly***

***After S/C level vibration on 8/8/99, the first attempt to turn on WARP X-band downlink resulted in inability to achieve carrier lock on 8225.0MHz signal.  Situation stayed this way for apprx 24hrs.***
***Test personnel diagnosing situation observed persistent Frequency Shift of 6-7MHz of entire spectrum (QPSK spectrum as expected but frequency shifted),  however detailed analyzer printouts were not obtained.  XPAA was vindicated as the 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 ever since.  In between events some S/C bay doors were opened, closed and manipulation of cables on WARP 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).***

## X-Band Anomaly

***X-Band Anomaly***

***Detailed fault analysis of all WARP/RF Exciter elements conducted in late August/early Sept, no theory proved  conclusive. Report on anomaly was generated and distributed***
***Most likely suspect attributed to intermittent external cable between WARP MIC and RF Exciter Cards (loosened during spacecraft vibration), however, intercable harness inspection, moving the harness, and resistance measurement in both directions of all cabling was performed and determined no anomalies***

## Fault Analysis Performed

***Fault Analysis Performed***

***XPAA - eliminated as cause because problem persisted after input switched to output of WARP/MIC board. ***
***MIC Card - Discounted as cause via detailed fault tree analysis ***
***RF - Exciter Card - Discounted as cause via detailed fault analysis***
***WARP - MIC to RF Exciter harness discounted as cause after measurement and inspection performed on 9/11 showed it to be nominal***
***GSE - RF spectrum analyzer, receiver and bit sync never indicated a malfunction, discounted as cause***
***RF cabling between S/C and GSE - suspect and replaced with new cables, but no current  theory supports perfect spectrum frequency shift***

## X-Band RF Exciter Anomaly Impact on Mission

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

***Problem seems most reasonably attributable to the interface between WARP MIC and RF-Exciter Card***
***Does not effect ability of WARP to record and capture data***
***Does not effect ability of WARP to playback data via S-band contingency path***
***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 flight-validate X-band Phased Array Antenna***
*Could perform carrier only or RF tests only*
*BER and noise characterization would be extremely difficult to validate*
***Full validation of other technologies (EFF, PPT etc.) would also be delayed until needs of SVT were realized***

## Initial X-Band Anomaly InvestigationI&T Recommendations

***Initial X-Band Anomaly Investigation******I&T Recommendations***

***1)******	******Freeze state of S/C (WARP) and record on GSE measured spectrum if problem recurs-   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 recur - Over 150 X-band downlinks performed, no recurrence of problem.***
***5)******	******Insert WARP - X-band baseband GSE into test port of MIC in case problem recurs - performed, will allow for viewing of MIC baseband output should problem recur.***
***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 install new cable between MIC and RF Exciter - NOT performed due to schedule constraints for February launch.***

## Strategy for Resolving Problem If Occurrs On Orbit

***Strategy for Resolving Problem If Occurrs On Orbit***

***Utilize additional S-band ground stations to allow approximately 10 S-band downlinks per day***
***Allows for one combined three instrument  DCE to get to ground per day***
***Form tiger team to analyze downlink spectrum and make recommendations for changing ground equipment to accommodate change in frequency spectrum***
***Work with Scientific Atlanta to modify current receiver***
***May require new receiver to accommodate custom spectrum for EO-1 - estimate 2-3 months turnaround and  (200-300K  ROM cost)***
***Could possibly utilize new technology Digital Reciever being developed by AETD 564 to tune to right spectrum if problem recurs***
***WARP can be commanded to output image  data onto single I or Q channel if problem is a stuck clock or data bit on one of the two channels***

## New AETD Investigation Team

***New 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.”***

## Summary

***Summary***

***Thorough fault analysis performed over six week period after the single frequency shift anomaly occurred***
***Documented in a technical report***
*** ******Most likely cause was determined to be wiring harness which subsequently checked okay***
***All recommendations for I&T completed and in place***
***Problem has not recurred in over 300 cycles of WARP/RF Exciter (X-band downlinks) and numerous spacecraft moves***
***Flight and operational workarounds will allow  mission to continue to meet validation objectives if problem recurs on orbit***
***Recommendation is to fly as is unless review board can identify a credible, demonstrable, and definitive cause***