TIPS (09/20/07)Ilana Dashevsky1 NICMOS Defocus Mode Status Ilana Dashevsky (Commanding)

TIPS (09/20/07)Ilana Dashevsky2 Team Developers & Testers: Colin Cox Ilana Dashevsky Tom Donaldson Rob Douglas Mark Giuliano Tony Krueger Matt Lallo Jinger Mo Karla Peterson Christine Ritchie Alan Welty Engineering: Morgan Van Arsdall (GSFC) John Bacinski (GSFC) Tom Wheeler Planning & Scheduling: George Chapman Beth Perriello Tony Roman Science & Data Analysis: Tommy Wiklind Helene McLaughlin Nor Pirzkal Ron Gilliland Eddie Bergeron Anton Koekemoer

TIPS (09/20/07)Ilana Dashevsky3 Goal Improve & simplify process to defocus the NICMOS detectors –Use Astronomer’s Proposal Tool (APT) and standard proposal processing to request a non-nominal focus for a detector Support planetary system investigations of very bright stars (up to S/N ~10,000) –Detect spectral features in planetary atmosphere using grism

TIPS (09/20/07)Ilana Dashevsky4 Ron Gilliland pioneered technique using NICMOS to observe stars like HD STScI PR : “Astronomers using NASA's Hubble Space Telescope have made the first direct detection of the atmosphere of a planet orbiting a star outside our solar system and have obtained the first information about its chemical composition.” - Team led by D. Charbonneau used STIS

TIPS (09/20/07)Ilana Dashevsky5 Rationale for Change Old implementation required significant manual intervention and checking –“Restricted” mode not intended for GOs –Specify defocus as a delta offset from nominal requires expert knowledge –Mistakes may result in mechanism hitting hard stop Number of GO requests to defocus detector 3 increased from one in 2003 to six in 2007 More requests expected –Defocus detector 1 (narrow band photometry)

TIPS (09/20/07)Ilana Dashevsky6 Background Pupil Adjust Mechanism (PAM) is used to provide optical alignment for NICMOS science observations. –Maximum PAM Motion is +/- 10mm –Maximum Tip/Tilt +/ a-s All 3 detectors were originally designed to share a common focus Deformation due to the dewar thermal short has resulted in separate PAM focus positions: –PAM 1, 2 and 3 are the home locations corresponding to detectors 1, 2 and 3 respectively –PAM I is an intermediate position that results in acceptable focus for detectors 1 and 2 –PAM C is used for coronographic observations

TIPS (09/20/07)Ilana Dashevsky7 Life Time Concerns Addressed Tom Wheeler recently re-examined PAM usage & failure modes –12,533 PAM moves & 5,431,471 focus motor revolutions on orbit, as of April 2007 –Motor & gear-head assembly tested to ~3 billion motor revolutions; never failed –Bellows assembly tested to 100,000 compression/expansion cycles; never failed –Lubricant & other mechanical components have proven track record in spacecraft Component fatigue due to motor overheating –Engineers at Ball concluded that “fatigue is not a problem” –Mitigate in schedule by enforcing PAM cool-down periods –Monitor schedule for possible PAM motor overheating events

TIPS (09/20/07)Ilana Dashevsky8 Implementation New PAM out-of-focus positions –Detector 1: -3.0 mm (best focus at 1.8 mm) –Detector 2: -5.0 mm (best focus at 0.2 mm) –Detector 3: -0.5 mm (best focus at -9.5 mm) More robust defocus commanding implemented –Command PAM to an absolute position Flight Software verifies position and checks against soft stop All front-end systems changes installed –APT, VTT, TRANS, Commanding, SIAF, Science Operations Database, SMS Review Tool –APT Version 16.4 –Phase II Proposal Instructions Eng. Version 16.1

TIPS (09/20/07)Ilana Dashevsky9 APT Changes New apertures for each detector to adjust the FOV center for the out-of-focus motion –NIC1-FIXD, NIC2-FIXD, NIC3-FIXD New exposure value for existing NICMOS Optional Parameter –CAMERA-FOCUS = DEFOCUS PI should consult with Instrument or Contact Scientist –Available but Unsupported mode

TIPS (09/20/07)Ilana Dashevsky10 APT Example

TIPS (09/20/07)Ilana Dashevsky11 On Orbit Test Verify that the new PAM locations produce desired science data Proposal consists of two orbits: –1 st orbit repeats observations for HD (7.6 mag) using detector 3 and grism G141 –2 nd orbit repeats observations from the routine focus monitor of an open cluster NGC-3603 to verify defocus for all detectors using phase retrieval

TIPS (09/20/07)Ilana Dashevsky12 Status 1 st orbit executed on September 13 th –Brief analysis by Ron Gilliland confirmed detector 3 defocus & aperture were successfully implemented 2 nd orbit will execute September 21 st –Defocus tested for all NICMOS detectors 2006 old method 2007 new defocus parameter

TIPS (09/20/07)Ilana Dashevsky13 Results Coming soon to a TIPS near you ….