We report on the extensive tests to characterize the performance of the infrared detector arrays for the Infrared Camera (IRC) on board the next Japanese infrared astronomical satellite, ASTRO-F. The ASTRO-Fwill be launched early 2004 and the IRC is one of the focal plane instruments to make observations in 2-26μm. For the near-infrared observations of 2-5μm, a 512x412 InSb array will be employed, while two 256x256 Si:As arrays will be used for the observations of 5-26μum in the IRC. Both arrays are manufactured by Raytheon.
To maximize the advantage of the cooled telescope and extremely low background radiation conditions in space, the dark current and readout noise must be minimized. The heat dissipation of the arrays also has to be minimized. To meet these requirements and achieve the best performance of the arrays, we optimized the array driving clocks, the bias voltage, and the supply currents, and evaluated the temperature dependence of the performance. In particular, we found that the voltage between the gate and source of the FET of the multiplexer SBRC-189 had a strong dependence on temperature. This effect becomes a dominant source for the noise unless the temperature
is kept within 20mK. We have achieved the readout noises of about 30e- and 40e- with the correlated double sampling for the flight model readout circuits of the InSb and Si:As arrays, respectively. These noises ensure that the background-limited performance can be achieved for the observations of IRC in the 4-26μm range in the current observing scheme.
In addition, we are now planning to make scan mode observations by IRC. We have developed a new operation way of the arrays to achieve the stable response and low readout noise in the scanning operation for the first time.
The IRC is now installed in the flight model cryostat and the first
end-to-end test has just been completed. We report on the expected performance of the IRC together with the array test results.