Calibration Status and Results for Wide Field Camera 3 Randy A. Kimble (GSFC) and the WFC3 Team HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
Outline • Purpose/potential of WFC3 • Configuration of instrument • Ambient and thermal-vac calibration results • Improvements in work – filters, crosstalk, IR detector • Future calibration plans HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
Key Team Members Supporting Calibration Science IPT (STScI) Detector Characterization Filter Evaluation Laboratory (GSFC) J. MacKenty S. Baggett B. Hill (also Science IPT) R. Boucarut T. Brown G. Delo P. Arsenovic H. Bushouse R. Foltz J. Kim Quijano D. Figer E. Malumuth M. Quijada G. Hartig A. M. Russell R. Telfer B. Hilbert A. Waczynski N. Reid Y. Wen M. Robberto • WFC3 also supported by Science Oversight Committee, chaired by Bob O’Connell/University of Virginia HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
Origins/Purpose of WFC3 • WFC3 originated when HST’s nominal observing lifetime was first extended from 2005 to 2010: facility instrument conceived for installation during Servicing Mission 4, to extend and enhance HST’s imaging capability • If SM4 approved, era of WFC3 operation now likely to be late 2007/2008 2013 and beyond? • WFC3 has been designed as a powerful general purpose camera: – widest spectral coverage of any HST instrument – 200-1000 nm in UVIS channel; 850-1700 nm in IR channel – complementary to ACS HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
Key Aspects of WFC3 • Unique capabilities in the near-UV – 200 to 400 nm • Unique capabilities in the near-IR – without cryogen or mechanical cryocooler! – 850 to 1700 nm (though warm, HST is very powerful in this range) • Large and diverse set of filters and grisms: 63 UVIS, 16 IR • Very capable accompaniment to ACS in the red, with more filters, fresh start with respect to radiation damage, and greater tolerance of CTE degradation HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
WFC3’s Intended Destination WFC3 is intended to replace the extraordinarily successful but aging WFPC2 in its radial instrument bay. HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
Overall WFC3 Configuration B-Latch Dimensions: 7.5’ x 7’ x 3’ Weight: 907 lbs HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
WFC3 Interior Configuration HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
UVIS Channel Summary Key Properties • 200 – 1000 nm • 4K x 4K CCD mosaic (two 2K x 4K UV-optimized CCDs) • 0.04” x 0.04” pixels, 160” x 160” field of view The WFC3 UVIS channel will extend high-sensitivity, large-format imaging at HST’s sharp angular resolution to the near UV. Relative fields of view of HST’s NUV imagers HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
UVIS Channel Science Goals NUV Observations Probe Age of The UVIS channel will be Stellar Populations particularly well suited to the study of: • Star formation history of galaxies (see figure at right) • Chemical enrichment history of galaxies • Ly α dropouts at z = 1 – 2. • It will also probe one of the darkest spectral regions of the natural sky background (~200 nm). HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
CCD Detectors • The WFC3 CCDs, developed by Marconi (now e2v) are shown in their flight housing (left) and mounted in the instrument (right). • The end-to-end read noise for the flight CCDs and electronics is 3 e- rms for all four readout amplifiers. HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
IR Channel Summary Key Properties • 850 – 1700 nm • 1K x 1K HgCdTe array with 1.7 micron cutoff • 0.13” x 0.13” pixels, 139” x 123” field of view • zodiacal-background-limited sensitivity in broadband filters The WFC3 IR channel will provide a 10-20+ x increase in survey speed vs. NICMOS + cryocooler, with finer angular resolution and improved stability, photometric accuracy, Relative fields of view of HST’s IR imagers and cosmetics. HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
IR Channel Science Goals The IR channel will take advantage IR Color-Color Identification of of the dark IR sky in space to High-z Galaxies study: • Type Ia supernovae and the accelerating universe • High-redshift galaxy formation (high-z dropouts) – note the strong NIR color-color discrimination of high-z galaxies in the figure at right • Sources of cosmic re-ionization • Dust-enshrouded star formation • Water and ices in the solar system. HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
IR Detectors • The novel 1.7 micron cutoff wavelength of the IR array (left), developed by Rockwell Scientific, permits low-dark-current operation at a temperature of <150 K, achievable with thermo-electric cooling alone. • A cooled inner shield (center) within the detector housing (right) helps to minimize the thermal background radiation incident on the array. HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
Ambient and Thermal-Vac Calibrations Performed • During “cancellation period” of 2004, instrument was fully integrated in a “non-final” mode, in which a number of hardware issues were tagged as “liens”, but not closed out • We targetted a “performance characterization” in which WFC3’s performance could be demonstrated for the purposes of contemplating non-HST use • Extensive suite of tests and calibrations performed, both in ambient and thermal-vac conditions – Ambient tests of UVIS channel – Thermal-vac tests of both channels – 1 st opportunity for end-to-end look at IR channel – Not a full science calibration, but all critical performance issues examined HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
Flight Subsystems Integrated for End-to-End Testing in 2004 HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
Thermal/Vac Test Setup Optical Stimulus Cryopanels WFC3 RIAF HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
Thermal/Vac Performance Highlights • Overall instrument performed very well – never came up to air for an instrument issue • 13,000 images obtained, assessing all aspects of WFC3 performance • Detailed results documented in several dozen Instrument Science Reports – http://www.stsci.edu/hst/wfc3/documents/ISRs – Easy to find: STScI → HST → Instruments → WFC3 → ISRs • Results confirm the powerful performance of WFC3 across its wide spectral range HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
UVIS Results Characteristic CEI spec; goal Measured Dark current <20 e/pix/hour 0.2-0.4 e/pix/hour Read noise (rms) <4 e/pix; <3 e/pix 2.98-3.08 e/pix Linearity <5% deviation over 100-50,000 e <3% deviation Full-well >50,000 e/pix; >85,000 e/pix ~68,000 e/pix Encircled energy 250nm: >0.75; >0.80 in 0.20” 250nm: 0.78-0.81* 633nm: >0.75; >0.80 in 0.25” 633nm: 0.77-0.81* Cal System 10,000 e/pix in <10 min <1 min Uniform to <2x ~7x Filter ghosts <0.2% of incident in a ghost Up to ~15% Image stability <10 milli-arcseconds over 2 orbits 15-50 mas * Specs apply to performance with OTA. Measurements obtained with CASTLE require corrections for differences in the optical systems. 250nm EE likely to fall just below CEI requirement (~0.72). HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
UVIS Channel Shows Excellent End-to-End Image Quality 810nm 250nm Goals Specs 350nm 633nm 810nm HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
UVIS System Throughput UVIS throughput very close to or better than predictions HST Cal Conf -- Oct 27, 2005 Calibration Status and Results for Wide Field Camera 3 – R. Kimble/GSFC, randy.a.kimble@nasa.gov
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