Camera Description

The following is a list of the different sub-systems that constitute the camera:

• The dioptric objective (OD), consisting of 6 lenses, projects the FOV onto the CCD. The OD is equipped with calibration LEDs and two active thermal controls (probes and heaters) controlled by the spacecraft.

• The focal-box (BF) contains the four CCDs, the prism and the active thermal control of the CCDs. The e2v CCD42-80 (2Kx4K) CCDs (see Fig. 1) operate in AIMO and frame-transfer mode. Two CCDs are dedicated to each of the AS and the PF camera subsystems. The focal plane is divided into two parts with an offset of a few millimeters between each pair of CCD (for different PSF shaping).

• The front end electronics (EP) generate the clocks and biases for the CCDs, and performs processing on the video signal of pre-clamping and amplification. Connections to the CCDs are through flex cables.

• The thermal drains that cool the CCD and the front-end electronics (connected to dedicated radiators).

• The mechanical interface optimally focuses the CCDs . It consists of the BIF (interface mechanical piece) which contains all the mechanical parts including the shims (of different thickness) to optically align the CCD.

• The shield protects the CCDs against protons and cosmic rays and provides the mount for the EP boxes.

• Thermal components such as the MLI, thermal probes and heaters provide thermal regulation.

The manufacturers involved in the various design studies and realization of the project are:

• Sodern for the focal-box and dioptric objective.

• Soditech/Teuchos for the thermal and mechanical study.

• Alcatel Valence for the front-end electronics.

The laboratories that provided management and performed some of the design studies are:

• CNES (Centre National d'Etudes Spatiales) for the thermal and mechanical studies.

• IAS (Institut d'Astrophysique d'Orsay) for the prism and optical studies.

• LAM (Laboratoire d'Astrophysique de Marseille) for the optical studies.

• LESIA (Laboratoire d'Etude Spatiales et d'Instrumentation en Astrophysique) for the management, system and electrical studies.

3. THE CAMERA TEST BENCH

The test bench was developed at the Institut d'Astrophysique d'Orsay (IAS) where different facilities have been used.

The test bench has four separate parts:

• The vacuum chamber and the active thermal control (IAS facilities) cool and regulate various items including the focal plane which is stabilized to -55°C.

• The mechanical support for the camera and support electronics (IAS facilities) have X/Y axis motors that enables optical stimuli to be placed anywhere on the focal plane with an accuracy of 1^m.

• The optical bench has two test camera systems. One that measures the gap between the CCDs by simulating a star at a given "infinity" (the OD has a strong focal curvature). A wavefront analyzer allows control of the optical bench. The other for calibration that simulates a given field of view.

• The electrical test equipment and software that provides full control of the functions of the test bench and image acquisition. Some real time image processing (for quick-look) is available. All image data is stored on hard disk for later data analysis.

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