Recent improvements in industrial vision technology and products together with the increasing need for high
performance, cost efficient technical detectors for astronomical instrumentation have led ESO with the contribution of
INAF to evaluate this trend and elaborate ad-hoc solutions which are interoperable and compatible with the evolution of
VLT standards. The ESPRESSO spectrograph shall be the first instrument deploying this technology.
ESO's Technical CCD (hereafter TCCD) requirements are extensive and demanding. A lightweight, low maintenance,
rugged and high performance TCCD camera product or family of products is required which can operate in the extreme
environmental conditions present at ESO's observatories with minimum maintenance and minimal downtime. In addition
the camera solution needs to be interchangeable between different technical roles e.g. slit viewing, pupil and field
stabilization, with excellent performance characteristics under a wide range of observing conditions together with ease of
use for the end user. Interoperability is enhanced by conformance to recognized electrical, mechanical and software
standards. Technical requirements and evaluation criteria for the TCCD solution are discussed in more detail.
A software architecture has been adopted which facilitates easy integration with TCCD's from different vendors. The
communication with the devices is implemented by means of dedicated adapters allowing usage of the same core
framework (business logic). The preference has been given to cameras with an Ethernet interface, using standard TCP/IP
based communication. While the preferred protocol is the industrial standard GigE Vision, not all vendors supply
cameras with this interface, hence proprietary socket-based protocols are also acceptable with the provision of a
validated Linux compliant API. A fundamental requirement of the TCCD software is that it shall allow for a seamless
integration with the existing VLT software framework.
ESPRESSO is a fiber-fed, cross-dispersed echelle spectrograph that will be located in the Combined-Coudé Laboratory
of the VLT in the Paranal Observatory in Chile. It will be able to operate either using the light of any of the UT's or
using the incoherently combined light of up to four UT's. The stabilization of the incoming beam is achieved by
dedicated piezo systems controlled via active loops closed on 4 + 4 dedicated TCCD's for the stabilization of the pupil
image and of the field with a frequency goal of 3 Hz on a 2nd to 3rd magnitude star. An additional 9th TCCD system shall
be used as an exposure-meter.
In this paper we will present the technical CCD solution for future VLT instruments.