The Instrumentation Platform

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Any scientific instrumentation, regardless of whether it is manual or automatic, ground-based or space-borne, needs some basic supporting infrastructure in the form of:

• Structural support of the instrument, for example the satellite platform or a measurement structure with instrument stand.
• Environmental subsystems, keeping environmental parameters (for example temperature) within acceptable limits.
• Power supply and conditioning devices.
• Control subsystems. Anything from a simple switch to a sophisticated telecommand system.
• Monitoring subsystems. Anything from eyeball observations of an instrument reading to a complex telemetry system.
• Communication subsystems.
• Data processing and storage subsystems.

For space-borne instruments, many of these functions are provided by the spacecraft platform. In the ground-based case many of these requirements are often more relaxed due to a less-hostile environment and the proximity to the general infrastructure of human civilisation. However if unmanned measurement stations are deployed in a sparsely-populated area with a sub-arctic climate, some requirements on the instrument platform becomes as demanding as in the space-borne case. Thus the ALIS-project required a closer examination of the basic infrastructure than most ground-based facilities in the field. The required basic infrastructure for low-light imaging stations could to a large extent also be used by other instruments (not necessarily optical), or even in entirely different contexts. Thus, these efforts to provide a housing for the ALIS stations resulted in the concept of a Ground-based Low-light Imaging Platform (GLIP) which constitutes the major part of an ALIS station.

The GLIP was designed in such a way that it should be able to operate in the harsh climate of the Kiruna region without any manual attendance for a period of up to 8 months. It was a requirement to be able to monitor and control all necessary functions of the GLIP remotely, even if the normal means for controlling the station should fail. In the case of a total communication- and control failure, critical subsystems, such as heaters and sensitive detectors, should enter a safe survival mode. The station should furthermore be able to continue operation even if the control centre failed. Finally, the GLIP would be designed in a modular fashion, so that the various subsystems and instruments should be easy to replace for maintenance, etc. The major subsystems of the GLIP are described in the following sections; refer to the block diagram in Figure A.1.

Figure A.1: Block diagram of the Ground-based Low-light Imaging Platform. The acronyms are explained in Table A.1

Table A.1: Explanation of acronyms in Figure A.1.