Performance

Monitoring

Sensitivity

Spectral Resolution

Background

The primary background sources that affect COS observations are detector dark count, earthshine, zodiacal light, and airglow emission; neither of the COS detectors suffers from read noise. For more information on COS background performance see Section 7.4 of the COS Instrument Handbook. For information on high S/N observations of the geocoronal Lyman-alpha line, please see the COS Airglow page.

Detector Dark Count Earthshine Zodiacal Light Airglow Emission

Throughput

COS is considerably more sensitive than STIS and earlier-generation HST instruments at comparable spectral resolutions, particularly in the far ultraviolet. At FUV wavelengths, the peak effective area is ~3000 cm² near 1300 Å with the G130M grating. At NUV wavelengths, the peak effective area is expected to reach ~850 cm² near 2250 Å with the G230L grating.

For further information, see Section 5.1.1 of the COS Instrument Handbook.

FUV High Voltage History

The COS FUV detector is a high-gain, cross delay line microchannel plate (MCP) detector. In the following links we present the high voltage history of each segment.

FUV History

Date	Time	HV Level (counts)	HV Level (volts)	Description
3/27/03	00:00	178	-5292.82	FUV02 installed; voltage value not verified
6/4/09	21:05	0	-2500.00	First HV turn on: HVON
6/5/09	16:55	100	-4069.00	HV Ramp up to HVLOW
6/6/09	20:51	154	-4916.26	HV Ramp Up Step 1
6/8/09	17:32	160	-5010.40	HV Ramp Up Step 2
6/10/09	19:23	166	-5104.54	HV Ramp Up Step 3
6/12/09	17:25	172	-5198.68	HV Ramp Up Step 4
6/14/09	19:00	178	-5292.82	HV Ramp Up to HVNOM
8/5/09	00:00	169	-5151.61	Lowered both segments to decrease modal gain
8/6/09	12:00	178	-5292.82	Return to nominal value
8/12/09	00:00	169	-5151.61	Changed HVNOM to 169/167 from 178/175
12/21/10	04:00	178	-5292.82	Temporary HV increase to original values
12/21/10	09:29	169	-5151.61	Return to nominal value
2/27/12	12:00	143	-4743.67	HV Sweep with wavecal at new lifetime position
2/27/12	12:20	147	-4806.43	HV Sweep with wavecal at new lifetime position
2/27/12	12:40	152	-4884.88	HV Sweep with wavecal at new lifetime position
2/27/12	12:49	157	-4963.33	HV Sweep with wavecal at new lifetime position
2/27/12	13:04	169	-5151.61	HV Sweep with wavecal at new lifetime position
2/27/12	13:20	175	-5245.75	HV Sweep with wavecal at new lifetime position
2/27/12	13:39	169	-5151.61	Return to nominal value
2/28/12	03:29	155	-4931.95	HV Sweep with deuterium lamp at new lifetime position
2/28/12	07:59	169	-5151.61	Return to nominal value
3/19/12	00:00	143	-4743.67	HV Sweep with wavecal at new lifetime position
3/19/12	00:40	147	-4806.43	HV Sweep with wavecal at new lifetime position
3/19/12	00:55	152	-4884.88	HV Sweep with wavecal at new lifetime position
3/19/12	01:10	157	-4963.33	HV Sweep with wavecal at new lifetime position
3/19/12	01:30	163	-5057.47	HV Sweep with wavecal at new lifetime position
3/19/12	02:00	169	-5151.61	Return to nominal value
3/19/12	06:00	143	-4743.67	HV Sweep with wavecal at new lifetime position
3/19/12	06:15	147	-4806.43	HV Sweep with wavecal at new lifetime position
3/19/12	07:00	152	-4884.88	HV Sweep with wavecal at new lifetime position
3/19/12	07:30	157	-4963.33	HV Sweep with wavecal at new lifetime position
3/19/12	08:00	163	-5057.47	HV Sweep with wavecal at new lifetime position
3/19/12	09:00	169	-5151.61	Return to nominal value
3/19/12	18:10	143	-4743.67	HV Sweep with wavecal at new lifetime position
3/19/12	18:55	147	-4806.43	HV Sweep with wavecal at new lifetime position
3/19/12	21:00	152	-4884.88	HV Sweep with wavecal at new lifetime position
3/19/12	21:20	157	-4963.33	HV Sweep with wavecal at new lifetime position
3/19/12	21:50	163	-5057.47	HV Sweep with wavecal at new lifetime position
3/19/12	22:30	142	-4727.98	HV Sweep with deuterium lamp at new lifetime position
3/20/12	04:00	143	-4743.67	HV Sweep with wavecal at new lifetime position
3/20/12	04:15	147	-4806.43	HV Sweep with wavecal at new lifetime position
3/20/12	04:45	152	-4884.88	HV Sweep with wavecal at new lifetime position
3/20/12	05:30	157	-4963.33	HV Sweep with wavecal at new lifetime position
3/20/12	06:10	163	-5057.47	HV Sweep with wavecal at new lifetime position
3/20/12	06:30	169	-5151.61	Return to nominal value
3/22/12	20:00	147	-4806.43	HV Sweep with deuterium lamp at new lifetime position
3/23/12	01:00	169	-5151.61	Return to nominal value
3/25/12	00:00	162	-5041.78	HV Sweep with deuterium lamp at new lifetime position
3/25/12	18:00	169	-5151.61	Return to nominal value
3/26/12	00:00	178	-5292.82	Increased HV to compensate for gain sag
4/16/12	00:00	167	-5120.23	Target ACQ testing at new lifetime position
4/16/12	09:00	178	-5292.82	Return to nominal value
4/17/12	04:00	167	-5120.23	G140L Focus Sweep at new lifetime position
4/17/12	08:00	178	-5292.82	Return to nominal value
5/24/12	00:00	100	-4069.00	HV Recovery - Day 1
5/25/12	00:00	154	-4916.26	HV Recovery Day 2 - QE grid off
5/29/30	00:00	100	-4069.00	HV Recovery Day 3 - QE grid off
5/30/12	00:00	160	-5010.40	HV Recovery Day 4 - QE grid off
5/31/12	00:00	154	-4916.26	HV Recovery Day 5 - QE grid off
6/1/12	00:00	166	-5104.54	HV Recovery Day 6 - QE grid off
6/4/12	00:00	160	-5010.40	HV Recovery Day 7 - QE grid off
6/5/12	00:00	172	-5198.68	HV Recovery Day 8 - QE grid off
6/7/12	00:00	166	-5104.54	HV Recovery Day 9 - QE grid off
6/8/12	00:00	178	-5292.82	HV Recovery Day 10 - QE grid off
6/11/12	00:00	172	-5198.68	HV Recovery Day 11 - QE grid off
6/12/12	00:00	178	-5292.82	HV Recovery Day 12 - QE grid off; back to HVNOM
6/17/12	19:00	167	-5120.23	Target ACQ testing at new lifetime position
6/19/12	02:00	178	-5292.82	Return to nominal value
7/23/12	00:00	167	-5120.23	New nominal HV value of 167 at second lifetime position
8/15/12	22:00	178	-5292.82	TDS old G130M/G140L target at old position
8/16/12	01:00	167	-5120.23	Return to nominal values
8/24/12	11:00	178	-5292.82	TDS old G160M target at old position
8/27/12	09:00	143	-4743.67	HV Sweep with wavecal at same postion as previous test
8/27/12	10:05	147	-4806.43	HV Sweep with wavecal at same postion as previous test
8/27/12	10:15	152	-4884.88	HV Sweep with wavecal at same postion as previous test
8/27/12	10:30	157	-4963.33	HV Sweep with wavecal at same postion as previous test
8/27/12	10:45	169	-5151.61	HV Sweep with wavecal at same postion as previous test
8/27/12	11:00	175	-5245.75	HV Sweep with wavecal at same postion as previous test
8/28/12	03:00	157	-4963.33	HV Sweep with wavecal at same postion as previous test
8/28/12	03:20	167	-5120.23	HV Sweep with wavecal at same postion as previous test
8/28/12	03:30	169	-5151.61	HV Sweep with wavecal at same postion as previous test
8/28/12	03:50	172	-5198.68	HV Sweep with wavecal at same postion as previous test
8/28/12	04:00	175	-5245.75	HV Sweep with wavecal at same postion as previous test
8/28/12	04:45	178	-5292.82	HV Sweep with wavecal at same postion as previous test
8/28/12	18:30	147	-4806.43	HV Sweep with wavecal above the new lifetime position
8/28/12	18:40	157	-4963.33	HV Sweep with wavecal above the new lifetime position
8/28/12	19:00	167	-5120.23	HV Sweep with wavecal above the new lifetime position
8/28/12	19:20	172	-5198.68	HV Sweep with wavecal above the new lifetime position
8/28/12	20:00	175	-5245.75	HV Sweep with wavecal above the new lifetime position
8/28/12	20:30	178	-5292.82	HV Sweep with wavecal above the new lifetime position
8/28/12	21:00	167	-5120.23	Return to nominal values
1/6/14	04:00	171	-5182.99	Characterization of gain at LP3 (LOP1)
1/6/14	06:30	167	-5120.23	Return to nominal values
2/4/14	09:00	171	-5182.99	Testing placement of spectra at LP3 (LOP2)
2/4/14	14:50	167	-5120.23	Return to nominal values
7/7/14	0:00	178	-5292.82	Testing new HV Management (LENA4/13637)
7/7/14	11:57	167	-5120.23	Testing new HV Management (LENA4/13637)
7/7/14	12:04	178	-5292.82	Testing new HV Management (LENA4/13637)
7/7/14	12:32	167	-5120.23	Testing new HV Management (LENA4/13637)
7/7/14	12:40	178	-5292.82	Testing new HV Management (LENA4/13637)
7/7/14	13:08	167	-5120.23	Testing new HV Management (LENA4/13637)
7/7/14	13:15	178	-5292.82	Testing new HV Management (LENA4/13637)
7/7/14	14:00	167	-5120.23	Return to nominal values
7/16/14	10:08	171	-5182.99	G130M/1222 focus run at LP3 (LENA2/13635)
7/16/14	12:00	167	-5120.23	Return to nominal values
9/23/14	14:00	171	-5182.99	Cross-Dispersion Profiles, Flux, Flat Field at LP3 - 1222 (LCAL3/13932)
9/23/14	15:00	167	-5120.23	Return to nominal values
11/3/14		173	-5214.37
2/9/15		171	-5182.99	Voltage for 1222 for the move to LP3
2/9/15		167	-5120.23	Voltage for standard modes for the move to LP3

Date	Time	HV Level (counts)	HV Level (volts)	Description
3/27/03	00:00	175	-5245.75	FUV02 installed; voltage value not verified
6/4/09	21:05	0	-2500.00	First HV turn on: HVON
6/5/09	16:55	100	-4069.00	HV Ramp up to HVLOW
6/6/09	20:51	151	-4869.19	HV Ramp Up Step 1
6/8/09	17:32	157	-4963.33	HV Ramp Up Step 2
6/10/09	19:23	163	-5057.41	HV Ramp Up Step 3
6/12/09	17:25	169	-5151.61	HV Ramp Up Step 4
6/14/09	19:00	175	-5245.75	HV Ramp Up to HVNOM
8/5/09	00:00	167	-5120.23	Temporarily lowered voltage to 169/167 from 178/175 to match prelaunch gain
8/6/09	12:00	175	-5245.75	Return to nominal value
8/12/09	00:00	167	-5120.23	Lowered both segments to decrease modal gain
12/21/10	04:00	175	-5242.75	Temporary HV increase to original values
12/21/10	09:29	167	-5120.23	Return to nominal value
3/8/11	19:31	175	-5245.75	Increased HV to compensate for gain sag
7/27/11	12:00	167	-5120.23	Lifetime Position Characterization test
7/28/11	00:00	175	-5290.08	Return to nominal value
7/30/11	00:00	167	-5120.23	Lifetime Position Characterization test
7/30/11	15:57	175	-5245.75	Return to nominal value
7/30/11	17:45	167	-5120.23	Lifetime Position Characterization test
7/31/11	00:00	175	-5245.75	Return to nominal value
7/31/11	12:00	167	-5120.23	Lifetime Position Characterization test
7/31/11	15:50	175	-5245.75	Return to nominal value
7/31/11	17:45	167	-5120.23	Lifetime Position Characterization test
7/31/11	19:40	175	-5245.75	Return to nominal value
8/1/11	13:40	167	-5120.23	Lifetime Position Characterization test
8/1/11	19:12	175	-5245.75	Return to nominal value
2/21/12	04:59	167	-5120.75	Aperture Verification / Spectrum Placement test (FENA2)
2/21/12	06:43	175	-5145.75	Return to nominal value
2/27/12	12:00	142	-4727.98	HV Sweep with wavecal at new lifetime position
2/27/12	12:20	147	-4806.43	HV Sweep with wavecal at new lifetime position
2/27/12	12:40	153	-4900.57	HV Sweep with wavecal at new lifetime position
2/27/12	12:49	162	-5041.78	HV Sweep with wavecal at new lifetime position
2/27/12	13:04	168	-5135.92	HV Sweep with wavecal at new lifetime position
2/27/12	13:20	173	-5198.68	HV Sweep with wavecal at new lifetime position
2/27/12	13:39	175	-5245.75	Return to nominal value
2/28/12	03:29	151	-4869.19	HV Sweep with deuterium lamp at new lifetime position
2/28/12	07:59	175	-5245.75	Return to nominal value
3/12/12	03:00	167	-5120.23	Aperture Verification / Spectrum Placement test (FENA2)
3/12/12	06:00	175	-5245.75	Return to nominal value
3/19/12	00:00	142	-4727.98	HV Sweep with wavecal at new lifetime position
3/19/12	00:40	147	-4806.43	HV Sweep with wavecal at new lifetime position
3/19/12	00:55	153	-4900.57	HV Sweep with wavecal at new lifetime position
3/19/12	01:10	158	-4979.02	HV Sweep with wavecal at new lifetime position
3/19/12	01:30	162	-5041.78	HV Sweep with wavecal at new lifetime position
3/19/12	02:00	175	-5245.75	Return to nominal value
3/19/12	06:00	142	-4727.98	HV Sweep with wavecal at new lifetime position
3/19/12	06:15	147	-4806.43	HV Sweep with wavecal at new lifetime position
3/19/12	07:00	153	-4900.57	HV Sweep with wavecal at new lifetime position
3/19/12	07:30	158	-4979.02	HV Sweep with wavecal at new lifetime position
3/19/12	08:00	162	-5041.78	HV Sweep with wavecal at new lifetime position
3/19/12	09:00	175	-5245.75	Return to nominal value
3/19/12	18:10	142	-4727.98	HV Sweep with wavecal at new lifetime position
3/19/12	18:55	147	-4806.43	HV Sweep with wavecal at new lifetime position
3/19/12	21:00	153	-4900.57	HV Sweep with wavecal at new lifetime position
3/19/12	21:20	158	-4979.02	HV Sweep with wavecal at new lifetime position
3/19/12	21:50	162	-5041.78	HV Sweep with wavecal at new lifetime position
3/19/12	22:30	142	-4727.98	HV Sweep with deuterium lamp at new lifetime position
3/20/12	04:15	147	-4806.43	HV Sweep with wavecal at new lifetime position
3/20/12	04:45	153	-4900.57	HV Sweep with wavecal at new lifetime position
3/20/12	05:30	158	-4979.02	HV Sweep with wavecal at new lifetime position
3/20/12	06:10	162	-5041.78	HV Sweep with wavecal at new lifetime position
3/20/12	06:30	175	-5245.75	Return to nominal value
3/22/12	20:00	153	-4900.57	HV Sweep with deuterium lamp at new lifetime position
3/23/12	01:00	175	-5245.75	Return to nominal value
3/25/12	00:00	159	-5057.47	HV Sweep with deuterium lamp at new lifetime position
3/25/12	18:00	175	-5245.75	Return to nominal value
4/16/12	00:00	163	-5057.47	Target ACQ testing at new lifetime position
4/16/12	09:00	175	-5245.75	Return to nominal value
5/24/12	00:00	100	-4069.00	HV Recovery - Day 1
5/25/12	00:00	151	-4869.19	HV Recovery Day 2 - QE grid off
5/29/30	0:00	100	-4069.00	HV Recovery Day 3 - QE grid off
5/30/12	00:00	157	-4963.33	HV Recovery Day 4 - QE grid off
5/31/12	00:00	151	-4869.19	HV Recovery Day 5 - QE grid off
6/1/12	00:00	163	-5057.47	HV Recovery Day 6 - QE grid off
6/4/12	00:00	157	-4963.33	HV Recovery Day 7 - QE grid off
6/5/12	00:00	169	-5151.61	HV Recovery Day 8 - QE grid off
6/7/12	00:00	163	-5057.47	HV Recovery Day 9 - QE grid off
6/8/12	00:00	175	-5245.75	HV Recovery Day 10 - QE grid off
6/11/12	00:00	169	-5151.61	HV Recovery Day 11 - QE grid off
6/12/12	00:00	175	-5245.75	HV Recovery Day 12 - QE grid off; back to HVNOM
6/17/12	19:00	163	-5057.47	Target ACQ testing at new lifetime position
6/19/12	02:00	175	-5245.75	Return to nominal value
7/23/12	00:00	163	-5057.47	New nominal HV value of 163 at second lifetime position
8/15/12	22:00	175	-5245.75	TDS old G130M/G140L target at old position
8/16/12	01:00	163	-5057.47	Return to nominal values
8/24/12	11:00	175	-5245.75	TDS old G160M target at old position
8/25/12	09:00	142	-4727.98	HV Sweep with wavecal at same postion as previous test
8/25/12	10:05	144	-4759.36	HV Sweep with wavecal at same postion as previous test
8/25/12	10:15	153	-4900.57	HV Sweep with wavecal at same postion as previous test
8/25/12	10:30	162	-5041.78	HV Sweep with wavecal at same postion as previous test
8/25/12	10:45	168	-5135.92	HV Sweep with wavecal at same postion as previous test
8/25/12	11:00	172	-5198.68	HV Sweep with wavecal at same postion as previous test
8/25/12	03:00	153	-4900.57	HV Sweep with wavecal at same postion as previous test
8/25/12	03:20	163	-5057.47	HV Sweep with wavecal at same postion as previous test
8/25/12	03:30	168	-5135.92	HV Sweep with wavecal at same postion as previous test
8/25/12	03:50	169	-5151.61	HV Sweep with wavecal at same postion as previous test
8/25/12	04:00	172	-5198.68	HV Sweep with wavecal at same postion as previous test
8/25/12	04:45	175	-5245.75	HV Sweep with wavecal at same postion as previous test
8/25/12	18:30	144	-4759.36	HV Sweep with wavecal above the new lifetime position
8/25/12	18:40	153	-4900.57	HV Sweep with wavecal above the new lifetime position
8/25/12	19:00	163	-5057.47	HV Sweep with wavecal above the new lifetime position
8/25/12	19:20	169	-5151.61	HV Sweep with wavecal above the new lifetime position
8/25/12	20:00	172	-5198.68	HV Sweep with wavecal above the new lifetime position
8/25/12	20:30	175	-5245.75	HV Sweep with wavecal above the new lifetime position
8/25/12	21:00	163	-5057.47	Return to nominal values
6/24/13	16:00	169	-5151.61	Changed HVNOM from 163 to 169
1/6/14	00:00	163	-5057.47	Characterization of gain at LP3 (LOP1)
1/6/14	04:00	167	-5120.23	Characterization of gain at LP3 (LOP1)
1/6/14	06:30	169	-5151.61	Return to nominal values
1/30/14	16:00	163	-5057.47	Testing placement of spectra at LP3 (LOP2/13618)
1/30/14	21:00	169	-5151.61	Return to nominal values
2/4/14	9:00	167	-5120.23	Testing placement of spectra at LP3
2/4/14	14:50	169	-5151.61	Return to nominal values
7/7/14	0:00	175	-5245.75	Testing new HV Management (LENA4/13637)
7/7/14	11:57	163	-5057.47	Testing new HV Management (LENA4/13637)
7/7/14	12:04	175	-5245.75	Testing new HV Management (LENA4/13637)
7/7/14	12:32	163	-5057.47	Testing new HV Management (LENA4/13637)
7/7/14	12:40	175	-5245.75	Testing new HV Management (LENA4/13637)
7/7/14	13:08	163	-5057.47	Testing new HV Management (LENA4/13637)
7/7/14	13:15	175	-5245.75	Testing new HV Management (LENA4/13637)
7/7/14	14:00	169	-5151.61	Return to nominal values
7/15/14	19:00	163	-5057.47	Focus run and aperture placement at LP3 (LENA2/13635, LENA1/13634)
7/16/14	10:08	167	-5120.23	G130M/1222 focus run at LP3 (LENA2/13635)
7/16/14	12:00	169	-5151.61	Return to nominal values
7/21/14	0:00	175	-5245.75	Changed HVNOM from 169 to 175
9/8/14	17:26	163	-5057.47	G130M/1222 focus run at LP3 (LENA2/13635)
9/8/14	19:00	175	-5245.75	Return to nominal values
9/21/14	20:00	169	-5151.61	Additional visit of 13330 at previous Segment B HV value
9/22/14	00:00	163	-5057.47	Cross-Dispersion Profiles, Flux, Flat Field at LP3 (LCAL3/13932)
9/23/14	14:00	169	-5151.61	Additional visit of 13330 at previous Segment B HV value
9/23/14	15:00	163	-5057.47	Cross-Dispersion Profiles, Flux, Flat Field at LP3 (LCAL3/13932)
9/24/14	01:00	169	-5151.61	Additional visit of 13330 at previous Segment B HV value
9/24/14	05:00	175	-5245.75	Return to nominal values
9/24/14	07:30	163	-5057.47	Testing ACQs at LP3 (LENA3/13636)
9/25/14	00:00	175	-5245.75	Return to nominal values
2/9/15		167	-5120.23	Voltage for 1222 for the move to LP3
2/9/15		163	-5057.47	Voltage for standard modes for the move to LP3
1/18/16		169	-5151.61	Voltage increase due to gain sag for all modes at LP3
10/17/16		175	-5245.75	Voltage increase due to gain sag for all modes at LP3

LAST UPDATED: 06/17/2019

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Background

Throughput

FUV High Voltage History

FUV Segment A

FUV Segement B

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