Photogrammetrically measured distortions of a composite microwave reflector system in vacuum at ~90 K

ABSTRACT The MicrowaveAnisotropy Probe (MAP) Observatory, scheduled for a 2001 launch, is designed to measure temperature fluctuations (anisotropy) and produce a high sensitivity and high spatial resolution (better than 0.3° at 90 GHz.) map of the Cosmic Microwave Background(CMB) radiation over the entire sky between 22 and 90GHz. MAP utilizes back-to-back composite Gregorian telescopessupported on a composite truss structure to focus the microwavesignals into 10 differential microwavereceivers. Proper position and shape of the telescopereflectors at the operating temperature of'90 K is a critical element to ensure mission success. We describe the methods and analysis used to validate the in-flight position and shape predictions for thereflectors based on photogrammetric metrology data taken under vacuum with the reflectors at '-'90K. Contour maps showing reflector distortions were generated. The resulting reflector distortion data are shown to be crucialto the analytical assessment ofthe MAP instrument's microwavesystem in-flight performance.