Mala Mateen (Air Force Research Laboratory)
Keywords: Wavefront Sensor, GEO
Abstract:
We are developing a highly sensitive non-linear Curvature Wavefront Sensor (nlCWFS) which will make it possible to detect dim objects near geosynchronous satellites (GEOs). Current Space Situational Awareness (SSA) programs rely on laser guide stars (LGSs) to detect dim objects near GEOs. This is a problem since Department of Defense (DoD) policy [DDOI:3100.11] does not permit the use of LGSs for the detection of U.S. operational or foreign satellites without prior permission. The nlCWFS will be able to detect GEOs and nearby objects without the use of a LGS. The nlCWFS senses at the diffraction limit whereas currently used WFSs such as the SHWFS sense at the seeing limit. This difference awards the nlCWFS a gain in photon flux of (D/r0)2. The SHWFS allows interference of points separated only by a subaperture making it insensitive to low order modes. The nlCWFS, on the other hand, uses spatial coherence over the entire pupil making it sensitive to low order modes which dominate the atmosphere and scatter light within a close angular separation of a GEO where a dim object might be hiding. In order to find dim objects near a bright target it is important to obtain a high contrast ratio within a small angular resolution of the central PSF core. The PSF contrast obtained with the nlCWFS is two orders of magnitude better than the SHWFS. In this paper we present results from building the nlCWFS for the 6.5 m MMT Smithsonian Observatory. We outline our progress towards building an nlCWFS for the AFRL/RDS Optics Division 1.5 m telescope and show simulations comparing the nlCWFS with the SHWFS and the PYWFS.
Date of Conference: September 10-13, 2013
Track: Optical Systems