COS Tables

Detector Count Rate Restrictions

The ETC uses the current count rate screening restrictions, which are taken from Section 10.1 of the COS Instrument Handbook. If the observation will exceed any of the count rate restrictions, a warning message will be given in the output page. The count rate restrictions for the detectors are as follows:

COS Count Rate Screening Limits

Detector

Source type [1]

Type_of_limit

Limiting count rate [2]

FUV

Predictable

Global

15,000 per segment

FUV

Predictable

Local

0.666 per pixel or 40 per resel [4]

FUV

Irregular

Global

6,000 per segment

FUV

Irregular

Local

0.666 per pixel or 40 per resel [3], [4]

NUV

Predictable

Global

30,000 per stripe

NUV

Predictable

Local

70 per pixel

NUV

Irregular

Global

12,000 per stripe

NUV

Irregular

Local

70 per pixel

NUV

Predictable (Imaging)

Global

170,000 (over entire detector)

NUV

Predictable (Imaging)

Local

50 per pixel

NUV

Irregular (Imaging)

Global

68,000 (over entire detector)

NUV

Irregular (Imaging)

Local

50 per pixel

Detector Dark Background

The following table lists the dark count rate and read noise characteristics of the COS detectors as measured in ground tests.

Detector background count rates (per second) for COS

Detector

Mode

Dark Rate

Read Noise

counts \cdot s-1 \cdot pixel-1

counts \cdot pixel-1

FUVB

target ACQ

7.00 x 10-6

0

FUVA

target ACQ

6.34 x 10-6

0

FUVB

spectroscopic

4.15 x 10-6

0

FUVA

spectroscopic

3.34 x 10-6

0

NUV

-

1.22 x 10-3

0