venus observations flight readiness review (hst program 8659) 21 january 2003 post-frr release –...

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Venus ObservationsFlight Readiness Review

(HST Program 8659)

21 January 2003

Post-FRR release – 24 Jan 2003

2003 Venus Observation

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1.0 Introduction/Overview (Tony Roman)

2.0 FSW, S/C H/W Changes and Implementation (Brian Vreeland)2.1 FSW and/or S/C H/W Functional Changes2.2 FSW Software Structure/Resource Changes2.3 Supporting Ground System Changes2.4 Supporting Documentation Changes2.5 Release Messages2.6 Unit and Build Level Testing/Results2.7 System Level Testing/Results

3.0 Engineering Test / Installation (Regalado, Haskins)

3.1 Overview and Initial Conditions3.2 Script Review3.3 Differences between Flight and Test Configurations3.4 Operations Acceptance Testing/Results3.5 Timeline Review - MEGG

Agenda


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Agenda

4.0 Monitoring and System Impacts (Craig Tyler)4.1 On-orbit Validation / Monitoring4.2 System Impacts4.3 Supporting Operations Changes 4.4 Supporting PRD Changes4.5 Training Module Changes

5.0 Constraints and Restrictions Review (Craig Tyler)5.1 CARD

5.2 OLD

6.0 Contingency Planning (Tyler, Roman)6.1 Vehicle Contingencies6.2 Observation Contingencies

7.0 Engineering Support Requirements (Craig Tyler)7.1 Personnel7.2 Communications / Data7.3 CCS

8.0Liens / Issues (Craig Tyler)

9.0 Actions


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Engineering Team

STScI - Tony Roman, Merle Reinhart, Alan Patterson

OTA - Mike Wenz, Dennis Crain, Art Bradley

DMS – Jessica Regalado

FSW – Liher Lu, Mike Schaeffer, Brian Vreeland, Bill Keksz, Shirley Duhaney

PCS – John Wirzburger

EPS – Stan Krol

I&C – Harry Wynn

SI – Scott Swain

Thermal – Christine Cottingham

Safing – Ed Moy

HIT – Stuart Bozievich

Operations – Pataro, Cooper

VEST Team

Systems Management – Sujee Haskins, Randy Stevens, Craig Tyler


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1.0 Introduction / Overview

¤ Objectives• Explain Venus observing strategy

• Review areas of special concern with Venus observations and explain how these concerns are being addressed

• Determine if the implementation is correct and complete

¤ Background• Why is Venus Special?

» Venus is about 47 degrees from the Sun

» HST is normally not permitted to point within 50 degrees of the Sun

• Venus Observing Program History» In cycle 4, HST observed Venus with GHRS and WFPC2 (GO programs 4518 and

5783)

» In cycle 6, two GO Venus proposals (6607 and 6771) were approved by the TAC; and there was one GTO/WF2 program (6851) to observe Venus. All of these were cancelled by the Director shortly after phase 2 submission.

» In cycle 7, there was a GTO/STIS program (7581) to observe Venus. Much implementation work was done, but the program was then withdrawn by the PI.


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1.0 Introduction / Overview

¤ Background (continued)• Venus Observing Program History

» In cycle 9, the TAC approved GO program 8659 to observe Venus. This program was planned for June 2001 but did not execute due to the failure of STIS side 1 electronics.

» Program 8659 is now replanned for January 26, 2003

¤ Scientific Goals• High resolution STIS spectrum of Lyman-• Assess the abundance of deuterium in the Venus atmosphere

• Constrain models of Venus atmosphere and climate evolution

¤ Observing Strategy• Observe while Venus is near maximum elongation

» In cycle 11, there are two 10 day long windows separated by 6 months

• Observe while HST is in Earth’s shadow» A window of 11-13 minutes per orbit

• One HST orbit is sufficient to conduct observation

• Generic TDRSS scheduling will be employed» Real-time contacts may not be available during the observation


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1.0 Observing Strategy Details

¤ Which elongation?• Eastern: August 2002, Western: January 2003

• Both are possible, but Western is easier

¤ Eastern versus Western Elongation

Target Visibility

Shadow

Target Visibility

ShadowEastern Elongation:

Western Elongation:


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¤ Initial GS Acq at Venus+5º• A pointing 5 degrees from Venus and 51.01 degrees from the Sun.• Minimizes slew distance to Venus• Precautionary measure to protect against large pointing error after slew

¤ GS Acq at Venus¤ Venus science observation

• 4.25m exposure• STIS auto wave cal disabled

¤ Venus+5 º Observation Geocoronal Lyman- foreground and interplanetary Lyman- background.• 16m exposure• For subtraction from Venus Lyman-alpha line

Target Visibility

GS Pair Acq at Venus+5º

Slew to Venus

Target Visibility

Shadow

Single GS Acqat Venus

Observe Venus

Slew toVenus+5º

ObserveVenus+5º

GS Pair Acq at Venus+5º


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¤ Venus Data• Apparent magnitude: -4.4 Venus Appearance at Observation

• Sun angle: 46.00 degrees

• Surface brightness: +1.5 (average for 1 square arcsecond of illuminated portion of disk)

• Apparent diameter: 21.12 arcseconds

• Phase angle: 81.24 degrees

¤ While slewing away from Venus, the telescope will be exposed to sunlight while pointed inside the Solar Avoidance Zone for 2 minutes 30 seconds

¤ Because this observation requires the telescope to be pointed close to the Sun while in the Earth’s shadow, a macro was developed to change the Safemode response from Inertial Hold to Software Sunpoint. The Sunpoint sun angle limit was also changed from 46 degrees to 42 degrees to provide a margin for the expected 46 degrees at closest approach.


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2.0 FSW, S/C H/W Changes and Implementation

2.1 FSW and/or S/C H/W Functional Changes• DCR 1052• Venus Observation SPC Macros

• Load File - QVENUSB_0.TAB • Activation Macro at SPC Address 13000

• Set up six TMDIAGS to monitor the six Safe Test Response Modifications • Modify the Sunpoint Sun Cosine Limit from 46 to 42 degrees• Modify six Safe Test Responses from Inertial Hold to Software Sunpoint (w/o Load Shed)

• SBREHE - High Mode Body Rate Error• SSPCLEXE – SPC List Exhaust• SBMICE - BMIC• SEMBOPE - Earth-Moon Protection• SMHGATCT - HGA Torque Limit• SNELEAKE - Neon Leak tests

• Perform BMIC management for the modified Tables

• De-Activation Macro at SPC Address 13100• Set up six TMDIAGS to monitor the six Safe Test Response Modifications • Modify the Sunpoint Sun Cosine Limit from 42 to 46 degrees• Modify six Safe Test Responses from Software Sunpoint to Inertial Hold • Perform BMIC management for the modified Tables

• IP-33_Venus_Obs_Procedure.doc• Load QVENUSB_0.TAB, using TMDIAGS to verify the load• Execute the Activation and De-Activation Macros with additional TMDIAG of Sun Cosine Limit

for Verification.


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2.2 FSW Structure/Resource Changes - None

2.3 Supporting Ground System Changes - None

2.4 Supporting Documentation Changes - None

2.5 Release Messages• SSM064

• IP-33_Venus_Obs_Procedure.doc

• PNM_2002343125203.TXT


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2.6 Unit and Build Level Testing/Results - None Needed

2.7 System Level Testing/Results - All Tests Passed

• LMBLAB tests using:• FV022a with Current On-orbit RAM Patches

• Flight DIU Addresses

• CCS Data Base O06100, CCS Release d4.0.1.0.24

• PC-PCSSIM 43c

• LMBLAB Checkout of IP-33 Installation and Backout Procedures and Macros

• Six tests that place HST at Venus Observing Attitude and fail Safe Mode Tests to verify Sunpoint instead of Inertial Hold

• One test that places HST Boresight between the Normal Mode Sun Cosine Limit (32 deg.) and Venus Macro modified Sunpoint Mode Sun Cosine Limit (42 deg.), then go to Sunpoint to force a failure of the modified Limit.


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3.0 Engineering Test / Installation

3.1 Overview and Initial Conditions• SSM486 Flight Software Version 2.2 Release A, plus on-board patches, are

currently executing in VSS with H-Format programmable telemetry enabled

3.2 Script Review• Set up TMDIAGs to verify Venus SPC macros (1 min)• Uplink Venus SPC macros via table load (1 min)• Verify load via TMDIAGs (1 min)• Set up TMDIAGs to verify current sun protect limit (1 min)• Execute Venus macro and verify change in safing response via TMDIAGs (4 min).

» Uses Special Processor with pointer value 13000» TMDIAGs are loaded via Macro

• Load TMDIAG to verify new sun protection limit (1 min)• After completion of Venus Observation event, execute SPC macro to reset the

safing response back to Inertial Hold (3 min)» Uses special Processor with pointer value 13100

• Set up TMDIAG to verify reset of sun protection limit back to it’s original limit (1 min)


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3.3 FSW/Operations Acceptance Testing and Results Objective: To validate Venus macro installation and back-out procedure in an

operational scenario without impact to operations. The OAT was performed using STScI-provided test SMS.

• VEST Configuration for 01/08/03 (008)» NSSC-I/CDH1 FSW 7.5.4 (Flight version of Safing/suspend RTCs set is loaded)» DMU (A side configuration), DIUs (flight configuration), CPM1» PCS Simulator (Alpha) version 42B» PSEA powered on

• 486 FSW Configuration (current on-orbit)» FSW 2.2A installed with latest on-orbit patches» BMIC enabled» KA enabled» Telemetry ‘H’ Format» Safemode tests and macros enabled for the SMS testing

• CCS Ground Test Configuration» Primary, B-string:

• Ground System Software - CCS Version 4.01• C String, Database - PRD-O06100TQ1


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3.3 FSW/Operations Acceptance Testing and Results (continued)• Test Sequence:

» Load and execute Venus macro to configure safe mode response during Venus observation

» Regression test during Venus observing period » Executed and validated the Venus back-out procedure» Reactivate Venus macro and initiate Inertial Hold Safemode failure to verify safe mode

response

• Test Results» The Venus Observation installation and back-out procedures were successfully installed

and no problems were encountered during regression testing

3.4 Differences Between Test and Flight Configurations• NSCC-I in Normal Mode with standard PIT Interface enabled. NSSC-I stored

commanding not used.» No Impact

• Used simulated EPS system modeled in PCSSIM» Battery Pressure Safe Test was not enabled» No Impact


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3.5 Timeline Review• 1st Installation Opportunity @ 026/05:54:38 – 026/06:12:50

• 2nd Installation Opportunity for steps 1-4 @ 026/06:26:00 – 026/07:10:57

• Slew to Venus+5º starts at 026:08:15:28

• Slew away from the Venus activities starting at 026:10:56:08

• 1st Backout Opportunity @ 026/10:59:27 – 026/11:30:30

• 2nd Backout Opportunity @ 026/12:40:15 - 026/13:14:14

• Scheduling Information» No special commanding is required for STIS

» No special commanding is required for other SIs


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3.0 Engineering Test / Installation - MEGG3.0 Engineering Test / Installation - MEGG

1st Installation Op.


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3.0 Engineering Test / Installation - MEGG3.0 Engineering Test / Installation - MEGG3.0 Engineering Test / Installation - MEGG

2nd Installation Opportunity


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1st Opportunity to backout


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2nd opportunity to backout


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4.0 Monitoring and System Impacts

4.1 On-Orbit Validation / Monitoring• DMS will validate successful load of the safemode configuration macro

4.2 System Impacts• PCS, DMS, I&C, SI, EPS: None

• OTA: See contingency section

• THERMAL: » Waiver of CARD 3.1.7.3 (see Section 5.1)

• SAFING:» Temporary modification to responses of six safemode tests

» In FSW, reducing the Sunpoint Sun protection threshold limit to provide margin for Venus Observation

• PSEA BOD circuitry provides redundancy against Sun in the boresight within 38º


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4.0 Monitoring and System Impacts

4.3 Supporting Operations Changes• Ops Requests

» Ops Request #16894-0, Venus Observation Patch

» Ops Request #16893-0, Venus Observation Contingency to Command SWSP

4.4 Supporting PRD Changes• None

4.5 Subsystem Training Module Changes• None


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5.0 Constraints and Restrictions Review

5.1 CARD• The following operations constraints or restrictions are met:

» 2.1.4.4 Sunlight on Fixed Head Star Tracker (FHST) Shutter» 3.1.4.8 PCS FHST Protection From Earth, Moon, Sun

• One waiver is required:» 3.1.7.3 HST Sun Pointing Limits

• The HST sun angle as measured from the +V1 axis should not go below 50°. Excursions could raise the OTA baffle temperatures above their bake-out temperatures and out-gassing may result.

• 46° is required for the Venus observation• EM MOSES 1067 outlines the thermal impacts to prolonged sun angles <50°

– A nominal Venus Observation as outlined here should not violate any temperature limits

– An inertial hold safemode at sun angles <50° has the potential to violate OTA baffle temperature limits

• All activities for installation handled by FSW code design and procedure» 3.1.9.36 Memory Load Using STFS Type 9 Command» 3.1.9.38 Telemetry Diagnostic Address Sampling» 3.1.9.41 HST 486 Flight Software Background Memory Integrity Check

• All contingency procedures comply with the CARD

5.2 OLD• No operations limitations violated or waivers required in the procedures

» All activities for installation handled by FSW code design and procedure


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6.0 Contingency Planning

6.1 Vehicle Contingencies• HST safing while pointed within the SAZ

» Concern• If HST were to enter inertial hold safe mode while pointed within the SAZ, that could violate

thermal temperature limits on the OTA baffles

• After 15 minutes in sunlight at 46° sun angle the OTA baffles exceed their 121°C bake-out temperature limit (EM MOSES 1067)

» Precautions• Redirecting certain safemode tests such that conditions that would normally lead to inertial hold

leads to software sun point safe mode instead to prevent Sun in boresight


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6.1 Vehicle Contingencies• FGS exposure to Venus

» Concern• If the attitude error is large enough, an FGS could possibly see Venus and cause potential

bright light exposure to the FGS photo-multiplier tubes. The only feasible scenario is an RGA flex lead failure that leaves the gyro online.

» Precautions• Choose guide stars that are as far as possible from Venus

• The chosen guide star is magnitude 11.1 and will be about 16.2 arcminutes from Venus

» Analysis• Goodrich assessed PMT damage should a worst-case event occur resulting in an attempted

acquisition of Venus with an FGS (ref: Goodrich Memo A16-ST-2254)

• Goodrich reports the short-term effect of the Venus acquisition would be the temporary incapacitation of the PMTs due to dark count elevation. While the exact value is not available for the given intensity, literature quotes range from several to 48 hours for recovery (for any target).

• Goodrich performed a relative assessment of the long-term effects of Coulomb draw (charge depletion) while attempting to acquire Venus with an FGS. While it is hard to determine exactly how the FGS would behave if it attempted to perform an acquisition on Venus, depending on how long it spends with Venus in the FOV, you could see a decrease in reliability from 1-3%.

» Response• If SEs determine that there is a large attitude error, Software Sunpoint may be commanded via

COP 6.01A


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6.1 Vehicle Contingencies• Code Red GSFC Inclement Weather Situation

» Venus observation will be executed from SMS

» If potential weather situation is predicted, an early execution of the safing macro will be performed during good weather

» If sudden storm occurs, SEs will make best effort to support from SMOR or via phone


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6.2 Observation Contingencies• Problem Shortly Before Observation

» Concern• An unrelated problem may threaten the Venus observing window• In cycle 4, the Venus observation was originally lost due to an unrelated safing; but it was quickly replanned and

executed successfully• In May 2001, the current program was delayed due to the failure of the STIS side 1 electronics

» Remedy• The current Venus observation could probably be rescheduled within a couple of weeks after January 26• A reduction of exposure time or an additional orbit would be required• The Sun angle would be reduced to 44-45 degrees• There might be conflicts with other time critical observations• At 44° sun angle there would be 8 minutes of sunlight allowed before the OTA baffles reach their 121 bake-out limits

(EM MOSES 1067)

• Guide star acquisition failure» Concern

• If attitude error is greater than the search radius, the guide star acquisition could fail resulting in the loss of the science

» Precautions• The chances are minimized by the short 5 degree slew to Venus• In cycle 4, additional FHST maps were also inserted by GSFC; but now there are automatic FHST maps, so this is

not an issue• A guide star acquisition test was planned in advance

– Guide star ID is 00624100797.– Test successfully completed on July 15, 2002

• If Guide Star failure, then shutter will not open


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7.0 Engineering Support Requirements

7.1Personnel• Test Conductor - DMS• FSW, Safing, PCS, and Systems Management – monitoring in SMOR • GSM and Systems Administration– supporting SMOR • Normal SE on-call personnel• FOT - normal shift

7.2Communications / Data• Operations briefing will be conducted on CCL-50 starting at 026/06:00 GMT (01:00 AM

EST)• Circuit assignments:

» CCL-50 Primary circuit for Test Conductor and FOT» CCL-56 SE to FC circuit

• FRR Material is available on EDOCS web site

http://edocs1.hst.nasa.gov/doc/publish/mop/misopdoc.htm

7.3CCS• Prime Ops on “A” string• Back-up Ops on “G” string• CCS Release 4.01• OPS PRD O06100Q• FSW loads have been delivered to both prime and back-up strings


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8.0 Liens/Issues

• None


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9.0 Actions

• Tyler – Review potential Shuttle dual-shift operations impact on Venus observations – No conflicts

• Tyler – E-mail Final MEGG to Chris Wilkinson for review – Completed 1/23/03• Regalado – Review final SMS/MEGG and scheduled forward/return,

especially from 09:45 to 10:05 GMT, and seek additional coverage, if needed – Completed 1/22/03

• DMS, FSW, Safing, PCS, and Systems Management – verify access to CCS prior to weekend support – Completed 1/21/03

• TCS – review heating on top bays during previous Venus observations» The past thermal analysis performed for the Venus observation only addressed

the heating of the OTA baffles and light shield. There has been no formal analysis on the heating of the equipment shelf due to high sun angles. Christine Cottingham reports that it will not be a problem as long as the aperture door is closed at sun angles < 50 degrees during inertial hold for the following reasons:

• The tops of the equipment bays are double blanketed, externally and internally, which is more insulated than a lot of bay doors that get sun all the time.

• No equipment is attached to the tops of the bays.• PCS thinks we might have seen some short excursions to high sun angles during the

1999 ZGSP, and no drastic temperature changes were seen in the bays.• At high sun angles the bay doors cool off due to low sun incidence on the bay doors. This

would provide a sink for the bays to reject extra heat.

» If an inertial hold is seen at high sun angles, TCS would closely monitor the situation. If temperatures were trending to where TCS thought there would be a problem, the spacecraft could be commanded to software sunpoint.

• For future Venus observations, unless there is a clear science gain schedule visits during daytime/weekday

venus observations flight readiness review (hst program 8659) 21 january 2003 post-frr release –...

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