COS Instrument Handbook for Cycle 25
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Cosmic Origins SpectrographInstrument Handbook for Cycle 25 > Chapter 1: An Introduction to COS > 1.3 COS Quick Reference Guide

1.3
Table 1.1: COS Instrument Characteristics
~0.11 arcsec per pixel1
(G130M along-dispersion2)

1
Exact value of plate scale depends on grating and lifetime position.

2
Raw plate scale.

Table 1.2: COS Detector Characteristics
Cs2Te (semi-transparent)
MgF2 (re-entrant)
85 10 mm (two)
25.6 25.6 mm
16,384 1024 (two)
1024 1024
16,384 128 (two, ACCUM)
16,384 1024 (two, TIME-TAG)
1024 1024
6 24 μm
25 25 μm
6 10 pix
3 3 pix
Typical dark-count rate (away from SAA)1
1.2 cnt s–1 cm–2
1.8 10–6 cnt s–1 pix–1
1.1 10–4 cnt s–1 resel–1
131 cnt s–1 cm–2
8.2 10–4cnt s–1 pix–1
7.4 10–3 cnt s–1 resel–1
Detector Global Count rate limit2
~1.67 cnt s–1 pix–1
~100 cnt s–1 resel–1
~200 cnt s–1 pix–1
~1800 cnt s–1 resel–1
7.4 μs

1
The dark rate varies with time. The reported values are measured as of October 2016. FUVA and FUVB values differ slightly (see Table 7.1).

2
Count rates higher than these limits will trigger a detector shut-down. Bright-object screening limits are lower. See Chapter 10.

3
The FUV values are not applicable to the COS FUV G130M blue cenwaves, 1055 and 1096. The local count rate limit for these two modes is 0.2 cnt s1 pix1.

Table 1.3: COS Calibration Accuracies
100:11

1
See Section 5.8.1.

Table 1.4: Useful Figures and Tables
HST focal plane and COS aperture

Cosmic Origins SpectrographInstrument Handbook for Cycle 25 > Chapter 1: An Introduction to COS > 1.3 COS Quick Reference Guide

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