We describe a new three-reflection telescope (TRT) prototype, where the 30-cm primary mirror is acting as the first and the third reflecting surfaces with different figurings. The two surfaces were realized and polished separately, and then accurately aligned and glued together. This technique has added more flexibility to the original design. The telescope provides: wide (2°x2° square degrees) corrected and unvignetted field of view, flat-field focal surface, small encumbrance, and easy access to the focal plane instrumentation. These characteristics make the TRT in combination with large area CCD cameras, a useful instrument for wide-field observations from remote and hostile ground sites, such as the Antarctic Plateau. The prototype has been equipped with a 2kx2k thermoelectric cooled CCD camera using the San Diego State University SDSU controller. A second custom controller prototype has been developed for ongoing space and Antarctica applications, characterized by synchronous fast readout capabilities (two 14-bit channels each sampled at 3.3 Msamples/s) and suitable to be scaled to large array mosaic applications. This project is aimed at the discovery and tracking of potentially hazardous NEOs, and identification of transient events such as GRBs.
In this paper we describe the solutions adopted for the design and the realization of an astronomical CCD imaging system, the results achieved on a Schmidt telescope (1 degree X 1 degree Field Of View, FOV) and, as well, the images obtained on a 30 cm prototype of a really innovative wide field telescope (2 degree X 2 degree FOV), a two-mirrors Three- Reflection Telescope (TRT), adopting aspherical reflecting- only surfaces. This solution allows the correction of every aberration, removing completely the vignetting and the field- curvature on very large fields of view (FOV). The CCD camera (equipped with a Loral 2k X 2k chip), operating under 'inverted mode' (Multi-Phase-Pinned mode, MPP), shows a dark current less than 0.1 e-/min at a temperature of only 200 degrees K. This particular operational mode enables the camera to provide accurate photometry even when the CCD is not at 'conventional' cryogenic temperatures. To cool-down the CCD chip it has been designed and realized a sophisticated Thermo- Electric-Cooler (TEC), which uses a three-stage Peltier module and glycol circulating in closed circuit at minus 10 degrees Celsius as heat exchanger. This TEC can reach, in this arrangement, an operative temperature of minus 80 degrees Celsius, approaching the typical performance of usual cryogenic systems. For its small encumber and for its reliability it is especially suitable for applications in which the room available is small, such as in internal-focus telescopes (e.g. Schmidt telescopes). Finally we briefly report new CCD and telescope projects.