FGS1r AMA Adjustment STScI/TIPS 02/19/09 Ed Nelan

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FGS1r AMA Adjustment

STScI/TIPS

02/19/09

Ed Nelan

Special Acknowledgements:

HSTMO, NASA/GFSC, Merle Reinhart , Denise Taylor, Matt Lallo,

Ed Kimmer (GSFC), Linda A-Reed (Goodrich), Mike Wenz, Art

Bradley, & the Guide Star Acquisition Working Group.

FGS1r AMA Adjustment: Motivation

• HST has a spherically aberrated primary mirror. FGS optics does not compensate for the spherical aberration.

• Small misalignment of FGS optics degrades interferometric response, and hence performance as a science instrument.

AMA

AMA

LOGO.049

Courtesy Linda A-Reed,

Goodrich

FGS1r AMA Adjustment

FGS1r AMA Adjustment

FGS1r AMA Adjustment

• Concerns & risks:

– AMA was last moved October 12, 1998.

– Does it still work?

– Can AMA failure lead to degradation or loss of FGS1r as a guider?

• GSFC convened a review of the proposed AMA move. Participants

– STScI

– GSFC

– MOSES

– Goodrich

• Approval to proceed granted after FMEA study indicated low risk.

FGS1r AMA Adjustment

• Prerequisites:

Determination of AMA move (Goodrich) based upon recently obtained FGS1r Scurves (from science programs 11212, 11943, 11944 )

 FGS1r OFAD re-calibration (proposal 11870 ), Dec 12 - 20, 2009

Preparation of phase2 ( 11964 ) proposal to verify OFAD across AMA move , and to provide data to update FGS1r-FGS alignment .

• Astrometric field in NGC 5617

• UCAC3 coordinates

• Yale proper motions (“special plate” ZZZT)

• Alignment shift of ~5” anticipated

Identification of post-AMA move target star to verify FGS1r S-curves are optimal

(proposal 11963 ).

 AMA move successfully executed Jan 22, 2009.

FGS1r-FGS Alignment NGC 5617 guide star pairs

FGS1r-FGS Alignment: finding the best pointing

FGS1r-FGS Alignment Preparations

• Phase2 proposal used “Spacecraft Pointing”, which specifies the

RA,Dec of the V1 axis (rather than a POS TARG on a star in FGS1r).

– easiest way to generate test visits in APT for finding good guide star pairs.

– once a good pointing was found, the S/C pointing was removed and replaced with the equivalent POS TARG in FGS to retain same pointing

FGS1r-FGS Alignment NGC 5617

FGS1r-FGS Alignment NGC 5617

FGS1r-FGS Alignment Preparations

• Phase2 proposal used “Spacecraft Pointing”, which specifies the

RA,Dec of the V1 axis (rather than a POS TARG on a star in FGS1r).

– easiest way to generate test visits in APT for finding good guide star pairs.

– once a good pointing was found, the S/C pointing was removed and replaced with the equivalent POS TARG in FGS to retain same pointing

– but, this made two of the guide star pairs invalid!!!!

– use of S/C pointing was put back in to regain the guide star pairs

• At SMS generation, S/C exposure lines resulted in “ illegal SMS ”.

– Merle Reinhart “fixed” this by manipulating post-SPIKE files.

– All worked out fine.

Post AMA-adjustment verification star, HD 233877

• Standard FGS calibration star known to be single (point source)

• Well isolated, tolerant of FGS1r-FGS alignment errors.

Results: S-curves

• AMA move successful!

– ~80% of misalignment along Y-axis removed.

– X-axis alignment undisturbed (as desired).

Results: FGS1r-FGS Alignment

As expected, ~5” shift of FGS1r in V2, small shift in V3.

– Courtesy Ed Kimmer (GSFC, SAC)

Results: FGS1r-FGS Alignment

• New FGS1r-FGS alignment matrix has been delivered to

STScI (from Ed Kimmer).

• Database updates planned for week of March 1.

• Since Jan 22, FGS1r has not been used as the “dominant guider”.

– The 5” misalignment would miss-point the telescope by that amount.

– FGS1r continues to be used successfully as a sub-dom (or roll control) guider.

FGS1r: post adjustment science:

GJ0860AB

NGC 3603, ACS

NGC 3603, FGS

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