Advanced Camera for Surveys: Status Update

1. Advanced Camera for Surveys:Status Update

2. Team News • Mark Clampin on Sabbatical (Nov 4)Thanks for a job well done! • Team Retreat (Oct 11) • Facilitate transition to a new Team Lead • Discuss current status ACS and future priorities • Calibration Workshop (Oct 17/18) • Summarize ACS status to the community & solicit feedback • Recognition • STScI Achievement Award: Jennifer Mack • GSFC SM3b awards Roeland van der Marel - Space Telescope Science Institute marel@stsci.edu http://www.stsci.edu/~marel

3. SMOV Closure Review(Sep 30) • ACS Requirements • Nearly all specs were met, many were exceeded. • Exception: misalignment/drift coronagraphic spots/mask • Coronagraphy • GTO and GO programs on hold • Commanding improvements implemented to minimize positional inaccuracies that affect scientific performance[Welty, Cox, Krist, Clampin] • New strategies still to be tested • Scheduling problem: prevent insertion of calibration observations (dark/bias) in a coronagraphy sequence. Roeland van der Marel - Space Telescope Science Institute marel@stsci.edu http://www.stsci.edu/~marel

4. Minor Instrument Anomalies • Image quality: • Long-wavelength halo WFC • PSF in UV has an asymmetric extension • SBC encircled energy slightly lower than hoped (due to unrealistic hopes [Hartig]) • Image drift: up to 5 mas/hr • Ghosts (low-level): • WFC CCD amplifier cross-talk: electronic ghosts • Optical ghosts Roeland van der Marel - Space Telescope Science Institute marel@stsci.edu http://www.stsci.edu/~marel

5. Minor Anomalies • Bias: • Variable offset between overscan and detector • Scattered Light: • Peculiar scattered light feature detected in some individual dark frames [reported by GOODS] Roeland van der Marel - Space Telescope Science Institute marel@stsci.edu http://www.stsci.edu/~marel

6. Hot Pixels • WFC Anneal Rate lower than for other HST CCDs • 80-85 % : WFPC2, STIS, ACS/HRC • 60-65 % : ACS/WFC • Continues to be monitored closely[Riess, van Orsow, Mutchler] Roeland van der Marel - Space Telescope Science Institute marel@stsci.edu http://www.stsci.edu/~marel

7. Measured Anneal Rate • Rate levels off as function of number of anneals Roeland van der Marel - Space Telescope Science Institute marel@stsci.edu http://www.stsci.edu/~marel

8. Hot Pixel Growth Rate • Long-term growthapproximately linear. Roeland van der Marel - Space Telescope Science Institute marel@stsci.edu http://www.stsci.edu/~marel

9. Hot Pixel Predictions(fairly uncertain) 1 hot pixel per4x4 box WFPC2 STIS no hot pixels 2002 2010 Roeland van der Marel - Space Telescope Science Institute marel@stsci.edu http://www.stsci.edu/~marel

10. Hot Pixel Impact • In the long-term, careful dithering will be essential • Hot pixels are always easier to remove than cosmic rays: you know where they are! Roeland van der Marel - Space Telescope Science Institute marel@stsci.edu http://www.stsci.edu/~marel

11. Hot Pixel Actions • Why is the anneal rate lower? • Possible cause [Clampin]: Integration in MPP mode, Read-out in non-MPP mode? ( no WFC3 impact) • What can be done about it? • Lower temperature (ASCS) ? • Tests will be done at higher T • Different annealing process (more often? longer? …) • Planned: Meeting of Detector Experts Roeland van der Marel - Space Telescope Science Institute marel@stsci.edu http://www.stsci.edu/~marel

12. Calibration • SIAF Tables updated (FGS re-alignment) [Cox] • Improved procedure for dark/bias frame creation [Mutchler, van Orsow] • Ongoing analysis of calibration data Roeland van der Marel - Space Telescope Science Institute marel@stsci.edu http://www.stsci.edu/~marel