1.3 COS Quick Reference Guide

Photocathode

CsI (opaque)

Cs₂Te (semi-transparent)

Window

None

MgF₂ (re-entrant)

Wavelength range

< 900–2150 Å

1650–3200 Å

Active area

85 × 10 mm (each for two segments)

25.6 × 25.6 mm

Pixel format (full detector)

16,384 × 1,024 (each for two segments)

1,024 × 1,024

Image size recorded per spectrum

16,384 × 128 (each for two segments, ACCUM)
16,384 × 1,024 (each for two segments, TIME-TAG)

1,024 × 1,024

Pixel size

6 × 24 μm

25 × 25 μm

Spectral resolution element size (= resel)

6 × 10 pix

3 × 3 pix

Detector quantum efficiency

~26% at 1335 Å
~12% at 1560 Å

~10% at 2200 Å
~8% at 2800 Å

Typical dark-count rate (away from South Atlantic Anomaly)¹

1.38 counts s^–1 cm^–2
1.99 × 10^–6 counts s^–1 pix^–1
1.19 × 10^–4 counts s^–1 resel^–1

180.80 counts s^–1 cm^–2
1.13 × 10^–3 counts s^–1 pix^–1
1.02 × 10^–2 counts s^–1 resel^–1

Detector Global Count rate limit²

60,000 counts s^–1

770,000 counts s^–1

Local count-rate limit^2,3

~1.67 counts s^–1 pix^–1
~100 counts s^–1 resel^–1

~200 counts s^–1 pix^–1
~1800 counts s^–1 resel^–1

Screening limits for bright objects

see Table 10.1

Dead-time constant

7.4 μs

280 ns

Approximate detector plate scale⁴
(dispersion axis)

G130M: 22.9 milliarcsec pixel^-1

G160M: 24.3 milliarcsec pixel^-1

G140L: 23.0 milliarcsec pixel^-1

G185M: 24.3 milliarcsec pixel^-1

G225M: 24.3 milliarcsec pixel^-1

G285M: 24.3 milliarcsec pixel^-1

G230L: 24.3 milliarcsec pixel^-1

Approximate detector plate scale⁴
(cross-dispersion axis)

G130M: 100 milliarcsec pixel^-1

G160M: 90 milliarcsec pixel^-1

G140L: 90 milliarcsec pixel^-1

G185M: 23.8 milliarcsec pixel^-1

G225M: 23.1 milliarcsec pixel^-1

G285M: 24.4 milliarcsec pixel^-1

G230L: 24.0 milliarcsec pixel^-1

Wavelength zero point: M gratings

15 km s^–1

15 km s^–1

Wavelength zero point: L gratings

150 km s^–1

175 km s^–1

Wavelength scale¹

15 km s^–1

15 km s^–1

Absolute photometry²

5%

5%

Relative photometry (same object at different times)²

2%

2%

Flat field quality (spectral S/N) per resel, using standard techniques

35:1

100:1

Flat field quality (spectral S/N) per resel, using special techniques

100:1³

100:1

Usage planning

Table 5.1

Grating parameters

Table 5.3

FUV grating wavelength ranges

Table 5.4

NUV grating wavelength ranges

Table 10.1

Count-rate screening limits

Aperture parameters and PSFs

Figure 3.2

BOA transmission

Figure 3.6

Model LSFs for the COS FUV channel

Figure 4.10

Model LSFs for the COS NUV channel

Figure 3.7

Resolving Power of FUV gratings

Figure 6.2

Relative throughput of the COS PSA in NUV imaging mode

Figure 6.4

Cross section of the COS imaging PSF

Figure 8.5

Relative transmission of the COS PSA in the NUV

Figure 13.29

HST focal plane and COS aperture

Effective Area

Figure 5.1

FUV spectroscopy

Figure 5.2

NUV spectroscopy

Figure 6.3

NUV imaging

Acquisitions

Figure 8.1

Examples of spiral search patterns

Figure 8.2

Point-source images with all apertures and mirrors

Figure 8.3

ACQ/IMAGE exposure times

Figure 8.4

Dispersed-light exposure times

Detector characteristics

Figure 4.1

FUV XDL detector schematic layout

Figure 4.9

NUV MAMA detector layout

Table 7.1

Detector background count rates

Overheads and observing parameters

Table 5.2

TAGFLASH exposure durations

Table 9.1

Overhead estimates for Phase I proposals

Table 9.2

Generic observatory overhead times

Table 9.3

Overhead times for OSM1 movements

Table 9.4

Overhead times for OSM2 movements

Table 9.5

Science exposure overhead times

Celestial backgrounds

Figure 7.1

Sky background versus wavelength

Figure 7.2

Moon, Earth and zodiacal-light background levels

Figure 7.3

Galactic extinction model

Table 7.3

Earthshine and zodiacal light fluxes

Table 7.4

Strengths of airglow lines

Data quality

Figure 5.13

FUV flat-field example

Figure 5.17

NUV flat-field example