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MAMBO PRE-LAUNCH CALIBRATION CONSIDERATIONS

MAMBO PRE-LAUNCH CALIBRATION CONSIDERATIONS. S. Gulkis Paris Meeting February 4-6, 2002. CALIBRATION OVERVIEW FOUR LEVEL WORK BREAKDOWN. RADIOMETRIC CALIBRATION SPECTRAL CALIBRATION TELESCOPE PARAMETERS BORESIGHT AND MIRROR POSITIONS. RADIOMETRIC CALIBRATION. Requirement

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MAMBO PRE-LAUNCH CALIBRATION CONSIDERATIONS

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  1. MAMBO PRE-LAUNCH CALIBRATION CONSIDERATIONS S. Gulkis Paris Meeting February 4-6, 2002

  2. CALIBRATION OVERVIEWFOUR LEVEL WORK BREAKDOWN • RADIOMETRIC CALIBRATION • SPECTRAL CALIBRATION • TELESCOPE PARAMETERS • BORESIGHT AND MIRROR POSITIONS

  3. RADIOMETRIC CALIBRATION • Requirement • brightness temperature between space and atmosphere known to within 1% (3) or noise level • RMS sensitivity less than 1 K in 1 sec • Calibration budget considerations • Optical system • Emissivity and temperature knowledge of calibration target • System linearity • Gain stability (Alan variance) • Sideband ratio • (calibration target and mirror alignment covered later) • Performance measurements • System temperature • Bandwidth

  4. SPECTRAL CALIBRATION • Requirement • Frequency knowledge to 1 m/sec - f/f < 1.0/3e8 = 3.3 e (-9) • Frequency stability to 3.16 m/sec - f/f < 3.16/3e8 = 1 e (-8) • Spectral response of filters /relative gain of spectral channels to 1% • Knowledge of sideband ratio to TBD % • Spectral budget considerations • USO and frequency synthesizers • Frequency response of spectrum analysers and filters • Including stability • Sideband responses /rejection • Temperature suceptabilities

  5. Wind Noise due to Frequency Jitter Requirement Frequency jitter shall produce an error less than .5 m/sec at 10 m/sec Implication for frequency stability f/f < 3.16/3e8 = 1 e (-8) Derivation |xm -xt| < 0.5 xm = measured wind speed = √(xt2 +x2) xt = true wind speed = 10 m/sec; x = freq. jitter (x/xt)2 = 2 (0.5)/xt x(rms) = 3.16 m/sec at xt = 10 m/sec Corresponds to 100 kHz at 10 Mhz √(102 +3.162)= 10.5

  6. Telescope Parameters • Requirements • HPBW TBD • Main beam efficiency >> 0.9 TBD • Sidelobe levels >> -30 db TBD

  7. BORESIGHT AND MIRROR POSITIONS • Requirements • Boresight direction shall known to within 0.2 HPBW and aligned with known WRT SC axis to within xxx • Boresight stability shall be within 0.05 HPBW • Considerations • Scan mechanism position, repeatability and jitter • S/C Stability

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