# Presentation: 514186

## Section 20

_***Section 20***_
***Command & Data Handling (C&DH)***

*** ******. . . Steve Schumacher***
*Swales Aerospace, Inc.*

*** ******. . . Philip Luers***
*NASA/GSFC*

## ACDS Contents

***ACDS Contents***

***Block Diagram (for reference)***
***Recent Activities***
***Residual Risk***
***Problem Reports***
***Special Topics***
***A/D converter anomaly***
***MOC timekeeping***
***Statement of Readiness***

## ACDS Box Block Diagram

- C&DH

- Power System Electronics (PSE)

- 1773 Fiber Optic Data Bus

- Inertial Reference Unit (IRU)

- Umbilical and APTS Racks

- Coarse Sun Sensors (4x)

- Three-Axis Magnetometer (TAM)

- Autonomous Star Tracker (AST)

- Reaction Wheels (RWA, 3x)

- Magnetic Torquer Bars (MTB, 3x)

- Reaction Control System (RCS)

- Pulsed Plasma Thruster (PPT)

- Solar Array Drive (SADA/ECU)

- Solar Array (Dep HTR and pot)

- GPS Receiver (GPS)

- HOP Actuators (HOPS)

- Light Flex Solar Array (LFSA)

- WARP Science Data Recorder

- S-band Transponder

- Spacecraft Heaters (Bays 1-6)

- Spacecraft Temperature Sensors

- Solar Array (Hinge pots and Htr)

- Solar Array Drive Temperature

***ACDS Box Block Diagram***

## “As Run” Verification Matrix

## Projected Power On Time

## ACDS Recent Activities (1 of 2)

***ACDS Recent Activities (1 of 2)***

***Recent changes to the verification matrix since the initial red team review***
***None***
***Configuration changes since the initial red team review***
***None***
***Recent test results associated with T/V II***
***Trending results showed no correlation of changes of voltage nor current with temperature of ACDS***
*4 temperatures, 4 voltages, 4 currents every 5 minutes for a total of 135,924 points*
***S/C timekeeping verification performed***
*GPS ON – verified to be identical in character to test results from 12/15/99*
*GPS OFF – verified to be identical in character to TV I results*

## ACDS Recent Activities (2 of 2)

***ACDS Recent Activities (2 of 2)***

***Technical peer reviews since the initial Red Team Review***
***None***
***Operating time since last modification***
***Total on time since beginning of environmental test***
*7/31/99 - 7/28/00: 2553 hours on spacecraft*
***On time since last modification (Interpoint power converter stiffener rework)***
*3/13/00 - 7/28/00: 679 hours on spacecraft*
***Open action items***
***None***

## ACDS Residual Risk

***ACDS Residual Risk***

***Remaining work to be completed***
***None***
***Open action items that are still being worked***
***None***
***Open test anomalies***
***None***
***Could-not-duplicate test anomalies***
***None***
***Redbook candidates***
***None***

## ACDS Problem Reporting

***ACDS Problem Reporting***

***Flight Hardware Issue***
***WOA 1095-20-5 185-15:09 RCS Tank Pressure telemetry point varying by 3 PSI.  Telemetry is toggling from 77F to 784 hex with no intermediate values  ***
*See A/D converter special topic.  Use as is.*
***Misinterpretation of test results by ACDS Lead***
***WOA 1099-20-23 Spacecraft time jumping erratically with GPS ON.  Behavior with GPS OFF is nominal***
*Magnitude of time jumps (with GPS ON) is 1-2 ms, mostly below 1 ms.  Review of test data from 12/15/99 showed that this is nominal behavior.  ACDS Lead did not have access to prior test data when PR was opened.  Requirement for spacecraft time to be no greater than 10 ms away from ground time is met with 80-90% margin.*

## Special Topic:

***A/D Conversion Anomaly***

*** ******. . . Harry Culver***
*EO-1 C&DH Systems Lead*

## Special Topic – A/D Converter

***A/D conversion anomalies during MAP MAC box-level thermal vacuum led to investigation***
***Stuck LSBs were found near A/D converter decision points (1⁄2-scale, 1⁄4-scale), referred to as “holes” in data  ***
*Readings of smoothly varying signals stick at point below decision point and then jump point above with no reading in between (for example 7F4 straight to 804)*
***All affected EO-1 subsystems in agreement at initial red team review that systems could be used as is***
*Investigation of cause was undertaken by GSFC Code 561*
***Performed extensive probing of MAP MAC housekeeping RSN ETU on extender card to identify character of signal***
***Modified software to perform various instructions before start of conversion, and during conversion, noted high correlation between instructions and noise on analog signals***

## Special Topic – A/D Converter

***Determined cause and recommended solution***
***ESN MCM (which includes microprocessor and analog in same package) has A/D converter analog signal input pin and instrumentation amp signal input pin interspersed with digital signals***
***Source of noise is coupling of instruction address and data bus onto A/D input and instrumentation amp input pins***
***MAP Flight Software engineer assisted in determining optimum instruction mix before start of conversion and during A/D conversion that made analog signals quietest and eliminated “holes” in A/D data.  Tested on MAP HK RSN and others.***
***Impact of flight software change to ACE, PSE, and HK RSNs was too great to implement at this point in program***
*All subsystems in agreement that use “as is” is best policy*
*Lowest 4 bits of A/D converter value are operationally unimportant*

## Special Topic:

***MOC Timing***

*** ******. . . Harry Culver***
*EO-1 C&DH Systems Lead*

## Special Topic – MOC Timing

***Verified proper operation of S/C timekeeping 12/99***
***S/C verified with GPS ON, within 1 ms of ground***
***S/C verified with GPS OFF, drift was measured and demonstrated compensation features of flight software***
***Testing of the ground system was not complete at time of initial Red Team Review***
***Ground station PTP generates ground time-tag of incoming “marked frame.”***
***MOC software compares ground time-tag with telemetered S/C time of “marked frame”.  Accounts for delays through flight system and ground system, and calculates difference to 1 ms resolution.***
***PTP was unable to time-tag data to high enough accuracy to meet 10 ms requirement***

## Special Topic – MOC Timing

***Ground station PTP hardware and software were modified***
***Fixed problems that arose due to telemetry sequence breaks***
***Ground station personnel assembled procedure for correct usage of PTP***
***Fixed drift problem with PTP***
***Performed retest of PTP in full ground station configuration 7/18/00 during Thermal Vacuum II***
***PTP version 1.49 software and drivers***
***Same time reference configuration***
***Operational MOC software***
***No retest required***

## Summary of Open Items from MarchRed Team Review

***Test and Verification flow -- no update necessary (page 19-13)***
***Verification Matrix -- no update necessary (page 19-14)***
***PR 797-70-02 Bus Buster showed non-uniform distribution of retries when run with minimal spacecraft bus traffic (page 19-16)***
***Further bus busting retest was performed following March Red Team Review with expected uniform distribution of retries***
***PR 818-20-02 MOC issued commands when not enabled for commanding (page 19-16)***
***MOC and I&T have successfully handed over dozens of times without confusion and loss of commands.  Issue resolved.***
***Updated operating hours are included in this package on page 20-5 (page 19-19).***
***Results of retest of Ground System time correlation verification (page 19-21 and 19-25).***
***Retest detailed in special topic.  Issue resolved.***

## Statement of Readiness

***The EO-1 ACDS is ready for shipping to VAFB and subsequent launch***