Pushing the Limits of the Coronagraphic Occulters on HST/STIS

Abstract

The Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) contains the only currently operating coronagraph in space that is not trained on the Sun. In an era of extreme--adaptive-optics--fed coronagraphs, and with the possibility of future space-based coronagraphs, we re-evaluate the contrast performance of the STIS CCD camera. The 50CORON aperture consists of a series of occulting wedges and bars, including the recently commissioned BAR5 occulter. We discuss the latest procedures in obtaining high contrast imaging of circumstellar disks and faint point sources with STIS. For the first time, we develop a noise model for the coronagraph, including systematic noise due to speckles, which can be used to predict the performance of future coronagraphic observations. Further, we present results from a recent calibration program that demonstrates better than $10^{-6}$ point-source contrast at 0.6", ranging to $3\times 10^{-5}$ point-source contrast at 0.25". These results are obtained by a combination of sub-pixel grid dithers, multiple spacecraft orientations, and post-processing techniques. Some of these same techniques will be employed by future space-based coronagraphic missions. We discuss the unique aspects of STIS coronagraphy relative to ground-based adaptive-optics--fed coronagraphs.

61 pages, 12 figures, accepted to JATIS

References in corpus (4)

• Fundamental limitations of high contrast imaging set by small sample statistics
• Probing for Exoplanets Hiding in Dusty Debris Disks: Disk Imaging, Characterization, and Exploration with HST/STIS Multi-Roll Coronagraphy
• New Debris Disks Around Nearby Main Sequence Stars: Impact on The Direct Detection of Planets
• Maximizing the ExoEarth Candidate Yield from a Future Direct Imaging Mission