JPCam conceptual design (credit: Fernando Santoro, J-PAS collaboration)

JPCam conceptual design (credit: Fernando Santoro, J-PAS collaboration)

The first light instrument for the JST250 telescope is JPCam, a 14-CCD mosaic camera using the new large format e2v 9.2k-by-9.2k 10μm pixel detectors. JPCam will be installed at the Cassegrain focus of the JST250 and will cover a large fraction of the telescope's FoV with a pixel scale of 0.2267 "/pixel.

JPCam is designed to perform the Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS), a photometric survey of the northern sky. The J-PAS survey strategy will use 56 filters, 54 narrow-band filters (~12.5nm) equi-spaced between 350 and 1000nm plus 2 broad-band filters to achieve unprecedented photometric red-shift accuracies for faint galaxies over ~8000 square degrees of sky.

JPCam filter system

Figure 1: JPCam filter system.

JPCam will consist of a mechanical and a camera subsystems. The camera subsystem comprises the cryostat, the cooling and vacuum systems, the CCD detector array, an optically powered entrance window and the electronics. The filter trays, the shutter and the interface with the telescope constitute the mechanical subsystem. The camera subsystem is being supplied by e2v under contract to the J-PAS collaboration.

The focal plane cold plane will include 14 large format CCD science detectors plus 12 auxiliary detectors located in the border of the field of view for guiding and image quality sensing and control.

Camera subsystem conceptual design (credit: e2v)

Figure 2: Camera subsystem conceptual design (credit: e2v).

JPCam focal plane layout (credit: e2v, CEFCA)

Figure 3: JPCam focal plane layout (credit: e2v, CEFCA).


The Filter Unit will be designed to admit five filter trays. Each filter tray will be easily and manually removable and exchangeable from the closed frame. Each one of the filter trays will contain 14 square filters each corresponding to the 14 CCDs of the mosaic. Each CCD will view only its corresponding filter. Figure 4 shows the mechanical structure conceptual design, housing the shutter and filter assembly. It is being designed and constructed by a Brazilian consortium led by INPE (Instituto Nacional de Pesquisas Espaciais). The massive 500mm aperture shutter is supplied by Bonn-Shutter UG.

JPCam FSU (credit: Fernando Santoro, J-PAS collaboration)

Figure 4: JPCam FSU (credit: Fernando Santoro, J-PAS collaboration).

Table 1. JPCam main performances
EE50 Ø =11 μm
EE80 Ø =22 μm
CCD format (14x) 9,216 x 9,232 pix, 10 μm/pix
Pixel scale 0.2267 “/pix
Read out time 12s
Read out noise 4 e- (RMS)
Number of filters 70