venus observations flight readiness review delta frr (hst program 12433) 19 january 2011

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Venus ObservationsFlight Readiness Review

Delta FRR(HST Program 12433)

19 January 2011

2010/2011 Venus Observation

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¤ Changes are in blue¤ Changed pages are:

• 3,10-12,16,25-27,48-57, 64

Changed Pages


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1.0 Venus Observation Tony RomanMerle Reinhart

2.0 FSW, S/C H/W Changes and Implementation Brian Vreeland2.1 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 / Installation3.1 Overview and Initial Conditions Ben Teasdel3.2 Script Review Ben Teasdel3.3 Standalone Testing Mike Wenz / Steve

Arslanian3.4 Timeline Review Ben Teasdel3.5 MEGG Ben Teasdel

Changed Pages


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Agenda

4.0 Monitoring and System Impacts Wayne Burdick4.1 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 Wayne Burdick5.1 CARD

5.2 OLD

6.0 Contingency Planning Wayne Burdick6.1 Vehicle Contingencies6.2 Other Contingencies

7.0 Engineering Support Requirements Wayne Burdick7.1 Personnel7.2 Communications / Data7.3 CCS

8.0 Liens / Issues Wayne Burdick

9.0 Forward Plan Wayne Burdick

10.0 Actions Wayne Burdick


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Engineering Team

STScI - Tony Roman, Merle Reinhart, Alan Welty, Charles Proffitt

OTA - Mike Wenz, Dennis Crain, Art Bradley

DMS / I&C– Ben Teasdel and Jessica Regalado

FSW – Brian Vreeland, Norm Roy, Shirley Duhaney, Suzanne Benedict, Susan Lien, Vicki van Duyl, Anthony Wells, Clive Caldwell, Linda Mitchell

Payload FSW - Dennis Garland

PCS – Dave Murphy

EPS – Stan Krol

SI – Scott Swain, Steve Arslanian

Thermal – Josh Abel

Safing – Ed Moy

Operations – Lynn Bassford, Joe Cooper

Systems Management – Wayne Burdick


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Objectives & Overview

• 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.

• Why is Venus Special ?• At its farthest, Venus gets to be about 47 degrees from the Sun.

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


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Venus Observing Program History

• In 1995, HST observed Venus with GHRS and WFPC2 (GO 4518 and GO 5783).

• In 1996, 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 STScI Director shortly after phase 2 submission.

• In 1997, there was a GTO/STIS program (7581) to observe Venus. Much implementation work was done, but the program was then withdrawn by the PI.

• In 2003, HST observed Venus with STIS (GO 8659).

• NASA program 12433 is now planned for:• December 27-28, 2010 (2010.361-362)

• January 22, 2011

• January 27, 2011


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Goals & Strategies

• Scientific Goals• Coordinated observing with ESA’s Venus Express mission.

• Map variations in SO2, SO, S2, and other UV absorbers.

• Constrain models of Venus atmosphere and climate evolution

• Observing Strategy• Observe while Venus is near maximum elongation

• Observe while HST is in Earth’s shadow• A window of 9-14 minutes per orbit

• Three visits of 2 orbits each.

• Originally to have also been coordinated with Atkatsuki mission, but that spacecraft failed to achieve Venus orbit


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Target Visibility

GS Pair Acq

at Venus+5D

Slew to Venus

Target Visibility

Shadow

GS Pair Acq at Venus+5D

Observing Strategy Details

• Initial GS Acq at Venus+5D• A pointing 5.5 degrees from Venus and 51.6 degrees from the Sun.• Minimizes slew distance to Venus• Precautionary measure to protect against large pointing error after slew

Observe Venus

Slew to Venus +5D

Single GS Acq at Venus

OBAD

Target Visibility

Slew to Venus

Shadow


Observe Venus

Slew to Venus +5D


OBAD


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Target Visibility

GS Pair Acq

at Venus+5D

Slew to Venus

Target Visibility

Shadow



• Single GS Acq at Venus• Saves about a minute versus pair acquisition

• Venus science observation• Visit 01: two 153s exposures, Visit 02: two 58s exposures, Visit 03: 116s

and 2.5s exposures• STIS auto wave cal disabled

Observe Venus

Slew to Venus +5D


OBAD

Target Visibility

Slew to Venus

Shadow


Observe Venus

Slew to Venus +5D


OBAD


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Venus Appearance at Observation

• Apparent magnitude: -4.1 +/- 0.2

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

• Apparent diameter• Visit 1: 28.5 arcseconds

• Visit 2: 21.4 arcseconds

• Visit 3: 20.4 arcseconds

• Phase angle• Visit 1: 97.3 degrees

• Visit 2: 89.9 degrees

• Visit 3: 79.4 degrees


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Vital Statistics

ObservationScience Exposure Time

Angle to Sun Limb (degrees)

Sunlit Time inside SAZ While Slewing Away from Venus Guide Star

January 1995 22-109s per orbit

46.3 2m 20s

January 2003 255s 46.0 2m 30s

Dec 28, 2010 orbit 1 153s 46.2 2m 14s (after GS time adjust)

S924000129 in FGS1on centerline

Dec 28, 2010 orbit 2 153s 46.2 3m 2s (after GS time adjust)

S924000129 in FGS1~50” from centerline

Jan 22, 2011 orbit 1 58s 46.1 1m 57s S8OF000650 in FGS112” from centerline

Jan 22, 2011 orbit 2 58s 46.1 1m 50s S8OF000650 in FGS1on centerline

Jan 27, 2011 orbit 1 116s 45.7 3m 12s S8L2000017 in FGS120” from centerline

Jan 27, 2011 orbit 2 2.5s 45.7 3m 2s S8L2047229 in FGS242” from centerline


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Areas of Concern

• Guide star acquisition failure

• Spacecraft or instrument problem shortly before scheduled observing time

• FGS exposure to Venus

• HST being exposed to sunlight while pointed within the Solar Avoidance Zone (SAZ)

• HST safing while pointed within the SAZ


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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.

• Too late to perform guide star acquisition test. Stars are in solar avoidance zone.

• Science exposures will proceed even if GS acquisition fails.• Special commanding specified to ignore “take data” flag.

• AQEXPIRE timer adjusted via SMS edit.

• Detector is protected because HST is in shadow• CCD is utilized for observation


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Problem Shortly Before Observation

• Concern• An unrelated problem may threaten the Venus observing window.

• In 1995, the Venus observation was originally lost due to an unrelated safing; but it was quickly replanned and executed successfully.

• The 2003 Venus observations were delayed from 2001 due to the failure of the STIS side 1 electronics.

• Remedy• Second choice coordination opportunity with Venus Express on January 23, 2011


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FGS Exposure To Venus

• Concern• If the attitude error is large enough (> 300 arcseconds), an FGS could

possibly see Venus and cause potential bright light exposure to the FGS photo-multiplier tubes.

• Precautions• Choose a guide star that is as far as possible from Venus.

• The chosen guide stars are:» Visit 01 : magnitude 12.4 and 15.5 arcminutes from Venus.

» Visit 02 : magnitude 11.7 and 16.8 arcminutes from Venus.

» Visit 03 : • Orbit 1: magnitude 11.2 and 13.8 arcminutes from Venus.

• Orbit 2: magnitude 11.5 and 12.5 arcminutes from Venus.


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FGS Exposure To Venus

• FGS PMT can tolerate and return to normal performance. • 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%.


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HST FOV – Visit 01


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HST FOV – Visit 02


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HST FOV – Visit 03 Orbit 1


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HST FOV – Visit 03 Orbit 2


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HST in the Sun

• Concern• While slewing away from Venus, HST will be exposed to sunlight and pointed

inside the SAZ for up to 3m 2s.

• HST’s maximum previous exposure to sunlight while pointed inside the SAZ was 2m 30s (2003 observation).

• Pointing inside the SAZ while HST is in sunlight can be tolerated for at least 15 minutes before the temperature of the paint inside the OTA would become a contamination issue. (EM-MOSES-1267 and EM-MOSES-1268)

• TCS has analyzed limits and has confirmed duration can be tolerated.

• Precautions• Guide star search radius was reduced in order to save 10-30 seconds of

acquisition time.


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HST Safing

• Concern• HST must not enter inertial hold safe mode while pointed within the SAZ.

• Precautions• Modifying the inertial hold safe mode response such that any condition that would

normally lead to inertial hold without closing the AD leads to software sun point safe mode instead.

• This was done in both prior HST observations of Venus.


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2010 Venus ObservationsGSACQ Adjustments

Merle Reinhart


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GSACQ Adjustments

¤ Idea is to compress the time allowed for the single-star GSACQs to minimize the time in sunlight within 50° of the sun and/or provide more science exposing time.

¤ Obvious places for a time compression are• Spiral Search time

• Move back to the target attitude (GS Offset via #43 command)

¤ STIS will ignore the TDF via special commanding. Thus, need to ensure if the GSACQ fails, that we are back at the target attitude for the science exposure.

• This implies a reasonable setting of the AQEXPIRE timer in the SMS call to the GSACQ PLCP.

¤ The AQEXPIRE changes are done as an SMS Edit.• If edit were to not occur, the only effect would be if the GSACQ failed, the

spacecraft would not be maneuvered back to the target position prior to the initiation of the Track51 for the exposure.


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GSACQ Time ReductionSpecifics – Jan 22 Visit

¤ Orbit #1• OBAD with Trackers 2 & 3 immediately prior to single-star gsacq

• Assumed error after the OBAD at the start of the gsacq is 20”

» Time for spiral search = 32s (-40s)

• At the target position, the guide star is 12” from the pickle centerline

» Time for 32” decenterline maneuver = 36s (-19s)

• Time for AQEXPIRE to fire and complete is 39s

» 31s for maneuver + 8s for other overheads

• Final GSACQ time = 344s + (-40s + -19s + 39s) = 324s

• AQEXPIRE value = 324s – 39s – 3s = 282s




• At the target position, the guide star is <1” from the pickle centerline







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GSACQ Time ReductionSpecifics – Jan 27 Visit




















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

FSW – Brian Vreeland


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2.1 FSW and/or S/C H/W Functional Changes• Venus Observation SPC Macros (DCR 1552)

• Load File – QVENUS0_0.TAB • Contains 2 Macros

• Activation Macro at SPC Address 19824 (Jump Table Addr 1)• Perform BMIC management for the modified Tables• 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

• Other Inertial Hold Test Responses Close AD in addition to IH and are not changed in macro

• SPSEAPSE - PSEA Power Supply Failure• SSUNAPRE - Sun Aperture • SSBOPE - Sun Bright Object Protection• Thermally safe if Aperture door is closed and HST is at 46 degress


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2.1 FSW and/or S/C H/W Functional Changes (cont…)

• Restoration Macro at SPC Address 19825 (Jump Table Addr 2)• Perform BMIC management for the modified Tables• Restore the Sunpoint Sun Cosine Limit from 42 to 46 degrees• Restores six Safe Test Responses from Software Sunpoint to Inertial Hold

• Installation and Usage Procedure “IP-219_Venus_Observation_Macros.docx”• 3 Sections

• Load, Dump and Compare QVENUS0_0.TAB, to verify the load• Execute the Activation Macro as required• Execute Restoration Macro as required


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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

• SSM212

• IP-219_Venus_Observation_Macros.docx

• PNM_20103473812.TXT

2.6 Unit and Build Level Testing/Results

• None Needed


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2.7 System Level Testing/Results

• Software Simulation Environment• 8 FVS tests run to verify proper configuration after macro execution

• VENOBS1 – Venus Observation Test 1 - Nominal Case• VENOBS2 – Venus Observation Test 2 - SPC List Exhaustion • VENOBS3 – Venus Observation Test 3 - BMIC Failure• VENOBS4 – Venus Observation Test 4 - High Body Rate Error• VENOBS5 – Venus Observation Test 5 - Earth/Moon Protection Error• VENOBS6 – Venus Observation Test 6 - HGA Torque Limit• VENOBS7 – Venus Observation Test 7 - Sun Cosine Limit• VENOBS8 – Venus Observation Test 8 - Neon Leak Case

• Verified that Software Sunpoint commanded versus Inertial Hold• Hardware Test Environment

• Lab Configuration• CCS 7.1.1.0.4 / PRD O07300R1S • PCSSIM 51A• On-Orbit Patches Installed• Gyro 3-4-5

• Installation Procedure Verification using VSSNOR and IP• Completed in LMB


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2.8 H/W Interfaces Impact & Verification Matrix• N/A

2.9 CPM2 & 3 Update Recommendation• N/A


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3.0 Engineering Test / Installation

• 3.1 Overview and Initial Conditions• SSM486 Flight Software Version 3.4 or higher and currently executing in VSS

with H-format programmable telemetry enabled

• 3.2 Script Review• Section A – Load, dump, compare Venus Observation SPC Macro Table Load

• Load Venus Observation SPC Macro Table load (1 min)• Dump the SPC table 1 (5 min)• Compare the Venus Observation SPC Macros Table with the dump (1 min)

• Section B – Venus Observation Macro Activation• Activate Venus Observation Macro 1 (1 min)

• Section C – Venus Observation Restoration• Verify Special Processor not active (1 min)• Activate post Venus Observation Macro 2 ( 1min)


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3.3 Standalone Testing • Objective

• To validate Venus macro installation and back-out procedure in an operational scenario without impact to operations. The Standalone Testing was performed using STScI-provided test SMS.

• DSTIF Test Bed Configuration• DMU (only one), DIUs (test configuration), CPM2

• PCS Simulator, Version 51A

• 486 FSW Configuration (current on-orbit)• FSW 3.4A installed

• BMIC enabled

• Telemetry ‘H’ Format

• Safemode tests and macros enabled for the SMS testing

• CCS Ground Test Configuration• Ground System Software – CCS Version 7.1.1.0.4

• Database – O07300R1S


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3.3 Standalone Testing (continued)• The STScI generated test SMS was run twice.

• Executed IP-219, Venus Observation SPC Macros, to patch the Safemode Responses and change the Sun Cosine Limit to support the Venus Observation

• During the first run of the SMS, the acquisitions were allowed to complete nominally.

• All of the acquisitions performed as expected.

• During the second run of the SMS, the acquisitions were forced to run long in the PCS Simulator to allow the AQEXPIRE timer to fire off.

• The setting of the AQEXPIRE parameter in the GSACQ blocks was verified to be long enough to allow enough time for the acquisitions to stop and maneuver the vehicle to the Target attitude before the Moving Target tracking slews were commanded.

• Executed IP-219, Venus Observation SPC Macros, to back out the Macro changes.

• If the AQEXPIRE command fires off while the #43 (Vehicle Offset Maneuver) command is being executed a Command Reject will occur.

• This is the same situation detailed in Ops Note 1973.• It takes a very unique failure case for this to occur.

• The Vehicle will be at the correct target location if this happens and there are no Health and Safety concerns. The acquisition will terminate correctly.


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STIS Venus Observations•Test SMS (STISITDF) was generated and delivered to the SISE to validate special commanding and confirm the CCD observations with the TDF response disabled, allowing the exposure to continue regardless of the results of the GSAcq

•All external CCD exposures are normally taken with TDF response enabled.

•Test SMS was executed on VSTIF on 12-2-10•NSSC-1 FSW BQ 9.0.8•STIS FSW CS5.01/MIE4.4 (ov0008) •Bus monitor tool enabled for logging•STIS Ops Benches in Safe mode prior to test start•SMS was executed twice, once with TDF enabled and once with TDF disabled•SMS transitioned STIS from Safe to Operate and then performed two CCD images. One with TDF response disabled and one with TDF Response Enabled.•CCD Images were then dumped and headers reviewed to verify CCD Shutter performance.


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STIS Venus Observations• Summary

• STIS CCD Shutter opens and closes normally regardless of TDF state when TDF response in disabled.

• Additional manual testing of STIS CCD shutter response to TDF state toggling while exposure in progress was also performed.

• CCD Shutter remained open.


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3.4 Timeline Review• 1st Opportunity to load Venus Observation Macros @ 356/20:28 – 20:55

• 2nd Opportunity to load Venus Observation Macros @ 356/21:56 – 22:37

• 1st Opportunity to activate Macro 1 @ 361/19:40 – 19:56

• 2nd Opportunity to active Macro 1 @ 361/21:36 – 22:01

• Slew to Venus+5º starts at 361/22:30

• Slew away from the Venus activities starting at 362/02:03

• 1st Opportunity to restore via Macro 2 @ 362/02:35 – 02:42

• 2nd Opportunity to restore via Macro 2 @ 362/03:35 – 03:40


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3.0 Engineering Test / Installation – MEGG review

PLACE HOLDER

1st opportunity to load Venus Observation Macros


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2nd opportunity to load Venus Observation Macros

1st op. for NSSCI load


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1st opportunity to Activate Macro 1


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2nd opportunity to Activate Macro 1


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1st opportunity to execute restore macro 2

2nd opportunity to execute restore macro 2


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3.4 Timeline Review

Venus Visit 1243302 • 1st Opportunity to activate Macro 1 @ 022/14:20- 14:50

• 2nd Opportunity to active Macro 1 @ 022/15:16 – 15:46



• 1st Opportunity to restore via Macro 2 @ 022/ 19:00 – 19:07


Venus Visit 1243303 • 1st Opportunity to activate Macro 1 @ 027/12:00 – 12:19

• 2nd Opportunity to active Macro 1 @ 027/12:28 -12:41



• 1st Opportunity to restore via Macro 2 @ 027/ 17:18 – 17:48



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2nd opportunity to Activate Macro 11st opportunity to Activate Macro 1


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2nd opportunity to Activate Macro 11st opportunity


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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

• PCS will monitor OBAD acq

• PI will validate data prior to Jan observations

4.2 System Impacts• PCS, SI, EPS: None

• DMS, I&C

• Mat LEI turned off for a 9 hour window

• 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• None

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• 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 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

• CDH Safing event

• Still activate observation macro

• Allow SMS to continue

• No observation


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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.

• Precautions

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

• The chosen guide star is magnitude 12.4 and will be about 15.5 arcminutes from Venus


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6.1 Vehicle Contingencies• FGS exposure to 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 6.01


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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 configuration 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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7.0 Engineering Support Requirements

• 7.1 Personnel• Test Conductor – DMS Ben Teasdel• FSW- Norm Roy• Systems Management- Wayne Burdick• STIS - Steve Arslanian• PCS - Dan Smith• Normal SE on-call personnel• FOT - normal shift

• 7.2 Communications / Data• FOT will be briefed before the test.• Circuit assignments:

• R/T Ops COORD Primary circuit for Test Conductor and FOT• HST COORD Backup loop to FOT

• Ops Requests (OR’s) • 18990 -4 – “Load Venus Observation Macros” • 18991-1 – “Venus Observation Patch” • 19000 -Venus Observation Patch 2• 19001 -Venus Observation Patch 3

• Flash Reports will be issued following completion of the test.• FRR Material is available on EDOCS web site

• http://edocs.hst.nasa.gov/MOP/Shared%20Documents/FRRpage.htm


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7.0 Engineering Support Requirements

7.3 CCS• Prime Ops on “F” string• Back-up Ops on “D” string• CCS Release 8.1.0.0.14• PRD O07300R1S• 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 Forward Plan

• Ops Briefing Jan 19th

• PI to analyze data from December observation prior to this briefing to ensure observation was successful and enable refinements of January observation to improve data gathering.


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10.0 Actions


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Backup Information


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Target

Visibility

GS Pair Acq

at Venus+5D

Slew to

Venus

Target

Visibility

Shadow

Single GS

Acq at Venus

Observe

VenusSlew to

Venus+5DObserve

Venus+5D

GS Pair

Acq at

Venus+5D


Target

Visibility

Shadow

Slew to

Venus

Single GS

Acq at Venus

Observe

VenusSlew to

Venus+5D

Observe

Venus+5D

GS Pair

Acq at

Venus+5D

–Display as seen from HST


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–Sun

–Venus

–Earth

HST’s View of Venus (t = 0)

–Venus is in Earth occultation. The Sun is not. HST would be pointed at Venus+5D at this time.

–Sun

–Venus

–Venus+5D–Earth

–Sun

–Venus

–Venus+5D–Earth


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HST’s View of Venus (t = 5 min)

–The Sun is moving toward setting.


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–The Sun is moving toward setting. The terminator becomes visible on the Earth.


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–The Sun is very close to setting.


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–The Sun has set. HST is now in the Earth’s shadow.


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–Venus is very close to rising. At about this time, HST will begin its slew from Venus+5D to Venus


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HST’s view of Venus (t = 30 min)

–Venus has risen. At about this time, HST will complete its slew to Venus; and the guide star acquisition will begin.


P. 7819 Jan 2011

LOGO.049


–At about this time, the guide star acquisition will finish; and the science observation will begin.


P. 7919 Jan 2011

LOGO.049


–At about this time, the science observation will finish; and the slew to Venus+5D will begin.


P. 8019 Jan 2011

LOGO.049


–The Sun is very close to rising.


P. 8119 Jan 2011

LOGO.049


–The Sun has risen. HST is now out of the Earth’s shadow. The slew to Venus+5D finishes a couple of minutes after sunrise.