The implementation of the 4MOST Facility at the ESO Paranal 4-meter VISTA wide-field telescope requires a substantial modification of the telescope. Since the current acquisition and guiding (A&G) and wavefront sensing optical systems (WFS) are embedded in VIRCAM and will be removed with it, replacements had to be provided. Although the A&G and WFS cameras will serve different purposes, they share common requirements. Among the shared requirements, a few are particularly challenging. For example, the environmental conditions the cameras will be exposed to require them to have an IP54 protection and due to their location, they cannot dissipate heat to the ambient air. To ensure optical alignment, the cameras must have very accurate housing and mechanical interfaces. In addition, both have to be integrated into an existing telescope control environment, with all that this entails in terms of service interfaces and protocols that can be used (e.g. GigE Vision), as well as operational requirements that must be met. After considering the specific performance requirements for the A&G cameras, the WFS detectors and the secondary guider sensor, a decision was made to use the same custom designed CCD camera model for all of them. These cameras are provided by Spectral Instruments. In this work we present the requirements for such cameras, their opto-mechanical design and the first results of their verification campaign, both at Spectral Instrument and AIP premises.
|