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3.4 Detector Subsystems

3.4.1 PHT-P

Subsystem PHT-P is a multi-filter, multi-aperture photopolarimeter with 3 single element detectors with wide beam (up to 3 arcmin) capability for faint extended sources. The wavelength coverage is in the range $\approx$ 3-130 ${\mu}$ m. The PHT-P detectors are each integrated in an integrating cavity and have a dimension of $1{\times}1{\times}1~$ mm³. Detector P1 is of Si:Ga, P2 of Si:B and P3 of Ge:Ga.

3.4.2 PHT-C

PHT C100 is a $3{\times}3$ array of Ge:Ga with $0.7{\times}0.7{\times}1~$ mm³ elements. Increased photon absorption is achieved by total reflection of a 30 $^{\circ}$ wedged pixel surface and an integrating cavity. The telescope beam is fed into these cavities by $1.9{\times}1.9~$ mm² anti reflection coated germanium fabry lenses mounted with spacing 100 ${\mu}$ m which results in an optical fill factor of 93%. The effective size of the pixels on the sky is $43.5{\times}43.5~$ arcsec², the distance between the pixel centers (`pitch') is 46.0 arcsec.

Throughout this manual the individual C100 pixels/detectors are labeled as in Table 3.1 where the +Z direction is upwards, and +Y is to the left. This corresponds to the projection of the array on the sky. The numbers (1...9) in Table 3.1 refer to the labeling and array counting in ERD, SPD and AAR products.

PHT C200 consists of 4 pixels arranged in a $2{\times}2$ matrix. The telescope beam is concentrated on the four detector pixels by anti-reflection coated germanium Fabry lenses of $3.9{\times}3.9~$ mm². The detector crystals are mounted in an integrating cavity and have prismatic shape to increase photon absorption. The sizes of the detector pixels themselves are approximately 1 mm³. The effective size of the pixels on the sky is $89.4{\times}89.4~$ arcsec², the distance between the pixel centers is 92.0 arcsec.

The pixels are stressed by individual screws; the stress is maximized to give a cut-off wavelength of 240 ${\mu}$ m. The labeling of the individual C200 pixels is given in Tables 3.2 and 3.3 for the ERD and SPD/AAR convention. The numbers (1...4) in the tables refer to the labeling and array counting in ERD, SPD and AAR products.

Table 3.1: C100 ERD, SPD and AAR pixel labels, +Z is up, +Y is left

9	6	3
8	5	2
7	4	1

Table 3.2: C200 ERD pixel labels, +Z is up, +Y is left

4	3
1	2

Table 3.3: C200 SPD and AAR pixel labels, +Z is up, +Y is left

4	2
3	1

3.4.3 PHT-S

PHT-S consists of a dual grating spectrometer with resolving power of order 90 in two wavelength bands. Band SS covers the wavelength range 2.5-4.8 ${\mu}$ m and band SL covers the range 5.8-11.8 ${\mu}$ m. Each spectrometer uses a linear array of 64 element Si:Ga detectors with dimensions of $0.31{\times}0.37{\times}1.80~$ mm³ per element. PHT-S has one entrance aperture which is square with dimensions $24''{\times}24''$ , this aperture is imaged onto each detector pixel. Two sides are parallel to the spacecraft Y axis, and the dispersion direction is in Z.

Next: 3.5 Fine Calibration Sources Up: 3 Instrument and AOT Previous: 3.3 ISOPHOT measurement concept

ISOPHOT Data Users Manual, Version 4.1, SAI/95-220/Dc