MRO high resolution imaging science experiment (HiRISE): Instrument test, calibration and operating constraints

EllisonHiRISE supports the Mars Reconnaissance Orbiter (MRO) Mission objectives through targeted imaging of nadir and off-nadir sites. Orbital images with high resolution and high signal to noise ratio will be obtained from Mars orbit. The images will have a scale of 25 to 32 cm per pixel from the nominal orbit of 250 × 320 km. HiRISE is a "push-broom" camera with a swath width at 300 km altitude of 6 km in a broad red spectral band and 1.2 km in bluegreen and near infrared bands. There are 14 CCD detector chips (2048 × 128 elements each) on the focal plane. The HiRISE camera has a half-meter primary mirror, yet through the use of lightweight glass optics and graphitecomposite structures, the mass of the instrument is only 65 kg. A uniform telescope temperature of20^°C is maintained and it's estimated orbital average power consumption is less than 60 W. The large data volume of a single nominal 20,000 × 40,000-pixel image requires 13 minutes to download to the spacecraft and hours to transmit to Earth. Optical alignment and testing is complicated by gravity sag in the lightweight structure and an IFOV of only 1.0 μrad. Low-noise CCD performance was attained at a rate of 16 Mpix/s. 128 levels of time delay and integration (TDI) is used to achieve a signal-to-noise ratio of > 150:1, but requires precision timing in the electronics and a quiet spacecraft.