Correlation of Target–dependent Calibration Methods used to Determine Absolute and Relative Radiometric Accuracy, Monitor Long–term Stability, Assess Stray Light Performance, Measure MTF Performance and Estimate Effective Focal Length for the IKONOS Space–based Remote Sensing Payload: Howard Bowen, James Erwin – ITT; Martin Taylor – GeoEye; Kurtis Thome – University of Arizona

ABSTRACT: The IKONOS remote sensing system has recently completed 8 years on-orbit. During that time several calibration methodologies have been employed to assess various performance parameters of the optical payload. Here we will present the results of an investigation that demonstrates the correlation between these several calibration methodologies incorporating vicarious ground, stellar and lunar targeting methods. Such correlations include: absolute radiometric accuracy; long-term radiometric stability; relative intra-band radiometric accuracy; relative inter-band radiometric accuracy; stray light assessment; MTF assessment; and, effective focal length determination.

Long–wave IR Spectroscopic Observations of Space Objects with the Broadband Array Spectrograph System (BASS) at the Advanced Electro–Optical System (AEOS) Telescope on Maui: Mark Skinner – AMOS Observatory; Ray Russell, Richard Rudy, David Lynch, Dee Pack, Kirk Crawford, David Gutierrez, Daryl Kim – The Aerospace Corporation

ABSTRACT: The Aerospace Corporation’s Broadband Array Spectrograph System (BASS) has been in use on calibration spectra of bright IR stars from two telescopes for over 10 years. Recently, mechanical and optical design work was accomplished to interface this sensor to the Advanced Electro-Optical System telescope on Maui. The design utilizes the existing f/200 chopping secondary and a Nasmyth mount on the yoke in concert with a reimaging off-axis parabola and secondary mirror system to convert the beam to the f/35 required to interface to the BASS dewar’s optical system. The ensemble includes a beamsplitter and additional optics operating in the visible to permit the use of a boresited CCD camera and filter wheel for both simultaneous guiding and to record images of objects of interest, such as comets, through visible filters from the Hale Bopp filter set. The interface was constructed at The Aerospace Corporation’s Space Science Applications Laboratory, assembled and tested in the laboratory there, then moved to the telescope for installation. First light was achieved in late 2005, using a new data acquisition system and software. The data system, which utilizes 115 individual analog to digital converters, one per detector element in the dewar, will also be described.

This interface expands our ability to obtain spectra of bright IR variable stars (see Russell et al. of this session for more in that area). We describe the design, and present data collected on a variety of space objects, including calibration stars, geosynchronous satellites, gamma ray burst optical counterparts, and space debris.

Calibrated Stellar Database of the USGS Lunar Calibration Program: Thomas Stone – US Geological Survey

ABSTRACT: The USGS program for lunar calibration has developed methods and models from a foundation database of telescopic observations of the Moon and stars collected by the RObotic Lunar Observatory (ROLO). Stellar extinction measurements are used to correct the lunar data for atmospheric transmission; consequently, star observations accounted for at least 70% of observing time during regular operations, which spanned more than 6 years. The ROLO database contains several hundred thousand individual star images in 32 wavelength bands in the solar wavelength range, 350 to 2500nm. Characteristics of the 190 ROLO target stars include: spectral types O through K, brighter than 6th magnitude, distribution over all equatorial angles, and mostly Northern Hemisphere declinations. Absolute calibration is based on observations of Vega and published reference flux and spectrum data. Uncertainty in the absolute scale is currently estimated ~5-10%, with the error budget dominated by the correction for the atmosphere. Ongoing refinements to ROLO data reduction algorithms are directed toward improving accuracy in stellar irradiance measurements, with the focus of current efforts on the areas of star image processing and extinction modeling.