Two-Gyro Science ImpactTwo-Gyro Science Impactand Observer Informationand Observer Information

Ken SembachKen Sembach

STUC MeetingSTUC Meeting

18-November-200418-November-2004

STUC Nov. 2004 KRS 2 / 17

Two-Gyro Handbook and WebsiteTwo-Gyro Handbook and Website• STUC comments are welcomedSTUC comments are welcomed

• HandbookHandbook• Central source of information about science and scheduling impacts Central source of information about science and scheduling impacts

of operating HST in two-gyro modeof operating HST in two-gyro mode• Released with the Cycle 14 Released with the Cycle 14 Call for ProposalsCall for Proposals• All necessary two-gyro information for Cycle 14 proposersAll necessary two-gyro information for Cycle 14 proposers

• Website Website ((http://www.stsci.edu/hst/HST_overview/TwoGyroMode)

• Site viewed frequently (>2700 top page hits since October 1)Site viewed frequently (>2700 top page hits since October 1)• Target visibility and orientation toolsTarget visibility and orientation tools• A narrated A narrated moviemovie showing sky availability for two-gyro and three- showing sky availability for two-gyro and three-

gyro modes over the course of a yeargyro modes over the course of a year• Links to two-gyro resources and HandbookLinks to two-gyro resources and Handbook

• >130 Handbook retrievals (pdf document) since October 1>130 Handbook retrievals (pdf document) since October 1• >1700 Handbook hits (all html pages) since October 1>1700 Handbook hits (all html pages) since October 1

STUC Nov. 2004 KRS 3 / 17

Two-Gyro Handbook Chapters1. Introduction2. Special Considerations for Cycle 143. The HST Gyroscopes4. Slewing and Pointing5. Guiding and Jitter6. Observation Planning7. ACS Performance in Two-Gyro Mode8. WFPC2 Performance in Two-Gyro Mode9. NICMOS Performance in Two-Gyro Mode10. STIS Performance in Two-Gyro Mode11. FGS Performance in Two-Gyro Mode12. Appendix A: Guide Star Magnitudes13. Appendix B: Quiescent F2G-FL Jitter Predictions

Instrument-specificinformation

Background information

Scheduling information

STUC Nov. 2004 KRS 4 / 17

STUC Nov. 2004 KRS 5 / 17

Overview of Two-Gyro Science Overview of Two-Gyro Science ImpactImpact

• Instrument Performance / JitterInstrument Performance / Jitter• Should be sufficient to conduct all but the most demanding Should be sufficient to conduct all but the most demanding

science observations (but there may be some demanding science observations (but there may be some demanding observations)observations)

• Expected jitter is not significantly larger than in three-gyro caseExpected jitter is not significantly larger than in three-gyro case• Full jitter characterization awaits on-orbit tests in FebruaryFull jitter characterization awaits on-orbit tests in February

• Scheduling of ObservationsScheduling of Observations• Less flexibility than in three-gyro modeLess flexibility than in three-gyro mode• Can be a serious impact for some observations, especially those Can be a serious impact for some observations, especially those

with orientation or timing constraintswith orientation or timing constraints• Several tools are available on the two-gyro website to assist Several tools are available on the two-gyro website to assist

with planning observationswith planning observations• Examples later in this presentationExamples later in this presentation

STUC Nov. 2004 KRS 6 / 17

Types of Observations That May Be Affected Types of Observations That May Be Affected By By

Entry into Two-Gyro ModeEntry into Two-Gyro Mode• Constrained ObservationsConstrained Observations

• Makes scheduling of observations more difficultMakes scheduling of observations more difficult• Roll angle constraintsRoll angle constraints• Timing constraintsTiming constraints

• CoronagraphyCoronagraphy• Not enough time to perform two acquisitions in an orbitNot enough time to perform two acquisitions in an orbit

• Precludes multiple roll angle positions in a single orbitPrecludes multiple roll angle positions in a single orbit• Jitter decreases light rejection performanceJitter decreases light rejection performance

• AstrometryAstrometry• Cannot schedule 180 degree separation of observationsCannot schedule 180 degree separation of observations

• Targets of Opportunity / Coordinated ObservationsTargets of Opportunity / Coordinated Observations• Generally time/position constrainedGenerally time/position constrained• Only ~50% of sky visible at any given timeOnly ~50% of sky visible at any given time

• Large observing campaigns like UDF / GOODS?Large observing campaigns like UDF / GOODS?• May be somewhat less efficient depending upon how scheduledMay be somewhat less efficient depending upon how scheduled• Roll angle restrictions may make tiling more difficultRoll angle restrictions may make tiling more difficult

STUC Nov. 2004 KRS 7 / 17

Instrument Performance / JitterInstrument Performance / Jitter• Jitter magnitude usually specified as RMS Jitter magnitude usually specified as RMS

deviation in 60 sec intervaldeviation in 60 sec interval

• Simulations indicate that pointing should be well Simulations indicate that pointing should be well within the 30x10 mas jitter ellipse requirementwithin the 30x10 mas jitter ellipse requirement

• Two-Gyro Handbook examples and exposure time Two-Gyro Handbook examples and exposure time calculators assume 30x10 mas ellipse to be calculators assume 30x10 mas ellipse to be conservativeconservative

• Point spread function analyses predict only modest Point spread function analyses predict only modest imaging/spectroscopic degradation even at this jitter imaging/spectroscopic degradation even at this jitter levellevel

• Changes in TChanges in Texpexp are also expected to be small are also expected to be small• Coronagraphic observations may be impacted and will Coronagraphic observations may be impacted and will

be characterized in the February on-orbit testsbe characterized in the February on-orbit tests

STUC Nov. 2004 KRS 8 / 17

Sample Two-Gyro Jitter Time Sample Two-Gyro Jitter Time SequenceSequence

1/4 sec time bins

Disturbance sequence above specified to test response of control law, not to mimic actual 800 seconds of observing time

STUC Nov. 2004 KRS 9 / 17

Sample Two-Gyro Jitter Projection Sample Two-Gyro Jitter Projection (sky plane)(sky plane)

ACS/HRC(~20% of time)

ACS/WFC(~80% of time)

STUC Nov. 2004 KRS 10 / 17

Jitter Predictions Jitter Predictions (including disturbances)(including disturbances)

GyroSet

Angle of GX Axis on Plane of

Sky

Maximum Boresight Jitter(mas, 60-second RMS)

mv = 9.58 mv = 13.0 mv = 14.5

Two-Gyro F2G-FL Results

1-2 0.0 9.55 9.76 10.40

1-4 -22.7 10.65 10.86 11.65

1-6 +22.7 11.72 11.91 13.06

2-4 +55.6 12.20 12.30 15.97

2-6 -55.6 12.39 12.47 17.41

4-6 +90.0 12.26 12.49 18.93 (+ LOL)

Three-Gyro Results

1-2-4 … 9.73 9.73 9.75

Most jitter will be well below maximum values listed above, even for faint guide stars.

STUC Nov. 2004 KRS 11 / 17

Effect of Jitter on the PSFEffect of Jitter on the PSF

Effect

Reduction in ACS PSF Central Flux

WFC(600 nm)

HRC(600 nm)

SBC(160 nm)

Detector Charge Diffusion

43%-59% 32%-45% …

PSF on Pixel Corner vs. Pixel Center

47% 19% 44%

OTA Breathing (+ 5 microns)

16% 10% 56%

Two-Gyro Jitter(30 x 10 mas RMS)

27% 42% ~50%

STUC Nov. 2004 KRS 12 / 17

Scheduling of ObservationsScheduling of ObservationsScheduling is likely to be more restrictive on science than Scheduling is likely to be more restrictive on science than

jitter.jitter.

Movie

3-Gyro

2-Gyro

Solar Avoidance

Unavailable region

Target availability changes with time

STUC Nov. 2004 KRS 13 / 17

Low Latitude Orientation Low Latitude Orientation Example Example

for Cycle 14for Cycle 14

z

Start of Cycle 14

3-gyro2-gyro (>30 min vis)2-gyro (<30 min vis)

STUC Nov. 2004 KRS 14 / 17

High Latitude Orientation High Latitude Orientation Example Example

for Cycle 14for Cycle 14

z

3-gyro2-gyro (>30 min vis)

Start of Cycle 14

2-gyro (<30 min vis)

STUC Nov. 2004 KRS 15 / 17

Examples of Programs that May be More Examples of Programs that May be More Difficult to Schedule in Two-Gyro ModeDifficult to Schedule in Two-Gyro Mode

• Time series observationsTime series observations• Supernova searches in known fields (e.g., GOODS)Supernova searches in known fields (e.g., GOODS)• Light curves (e.g., supernovae, Cepheids, GRBs, Light curves (e.g., supernovae, Cepheids, GRBs,

etc.)etc.)

• Roll-constrained observationsRoll-constrained observations• Experiments requiring same ORIENT for extended Experiments requiring same ORIENT for extended

periodsperiods• May affect efficiency of future Deep FieldsMay affect efficiency of future Deep Fields

• Large tiling programs making use of 180 degree roll Large tiling programs making use of 180 degree roll (e.g., recent large Orion mapping program)(e.g., recent large Orion mapping program)• Loss of efficiency would be main impactLoss of efficiency would be main impact

STUC Nov. 2004 KRS 16 / 17

Hubble Deep Field Hubble Deep Field Target Visibility in Cycle 14Target Visibility in Cycle 14

Observation

Date

Target Visibility

(minutes)

01-Nov-2005 47

14-Dec-2005

15-Dec-2005

16-Dec-2005

49

48

48

31-Jan-2006

01-Feb-2006

02-Feb-2006

53

52

51

14-Mar-2006

15-Mar-2006

16-Mar-2006

19

20

64

30-Apr-2006

01-May-2006

02-May-2006

06

06

06

09-May-2006

10-May-2006

11-May-2006

73

75

78

STUC Nov. 2004 KRS 17 / 17

Hubble UltraDeep FieldHubble UltraDeep Field Target Visibility in Cycle 14 Target Visibility in Cycle 14

3-gyro2-gyro

Observation

Date

Target Visibility

(minutes)

01-Jul-2005 46

15-Aug-2005 47

01-Oct-2005 47

15-Nov-2005 20

13-Dec-2005 45

14-27 Nov-2005 <30

>19-Dec-2005 <30