Format definitions

Boldface type indicates the name of an APT parameter or a value for a parameter.

Black text indicates an important note.

Magenta text indicates available but unsupported parameters (requires prior approval from STScI).

Red text indicates restricted parameters (for STScI use only).

Brown text indicates text file parameters.

Items in brackets - <value> - are required values.

Items in square brackets - [<value>] - are optional.

The following table specifies the legal COS spectral element/wavelength combinations for the COS/FUV and COS/NUV configurations. For information on the Lifetime Positions used for each central wavelength see Table 11.1 Lifetime Positions for Cycle 34 COS/FUV Science Observations through the PSA).

Table 11.7: COS Spectral Elements and Central Wavelengths

Configuration	Spectral Element	Central Wavelengths (Å)
COS/FUV	G130M	1055¹, 1096¹, 1222¹, 1291, 1300, 1309, 1318, 1327
	G140L	800¹, 1105, 1280
	G160M	1533¹, 1577, 1589, 1600, 1611, 1623
COS/NUV²	G185M	1786, 1817, 1835, 1850, 1864, 1882, 1890, 1900, 1913, 1921, 1941,1953, 1971, 1986, 2010
	G225M	2186, 2217, 2233, 2250, 2268, 2283, 2306, 2325, 2339, 2357, 2373, 2390, 2410
	G230L	2635, 2950, 3000, 3360
	G285M	2617, 2637, 2657, 2676, 2695, 2709, 2719, 2739, 2850, 2952, 2979, 2996, 3018, 3035, 3057, 3074, 3094
	MIRRORA³	N/A
	MIRRORB⁴	N/A

¹Target acquisition modes are not allowed with this central wavelength.

²Due to increased COS NUV detector background and mechanism position uncertainties, certain central wavelength settings have proven to be unreliable in the NUV ACQ/PEAKXD target acquisition phase. The central wavelengths settings that appear in bold are the preferred central wavelengths for STRIPE=DEF NUV ACQ/PEAKXD exposure. See the COS Instrument Handbook and Mode = ACQ/PEAKD Config = COS/NUV for details.

³The MIRRORA spectral element positions a flat mirror in the beam to produce an image of the sky with a field of view slightly larger than the diameter of the aperture. If you intend to produce an image and there are no bright object-concerns, use MIRRORA. Restricted for wavecals and forbidden for flats.

⁴MIRRORB attenuates the image and is suitable for use with bright objects. Restricted for wavecals and forbidden for flats.

Available but unsupported configurations at non-standard lifetime positions

Table 11.7: Additional configurations offered in AVAILABLE mode.

Spectral Element	Central Wavelength (Å)	LIFETIME-POS	Available for ACQs?	SEGMENT (DEFAULT)	FP-POS
G130M	1291	LP3	Yes	A, B, BOTH	1, 2, 3, 4, ALL
G130M	1300	LP3	Yes	A, B, BOTH	1, 2, 3, 4, ALL
G130M	1309	LP3	Yes	A, B, BOTH	1, 2, 3, 4, ALL
G130M	1318	LP3	Yes	A, B, BOTH	1, 2, 3, 4, ALL
G130M	1327	LP3	Yes	A, B, BOTH	1, 2, 3, 4, ALL

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11.5.1 COS Internal Calibration Targets
11.5.3 COS Apertures
11.5.4 COS WAVECAL Exposure Parameters
11.5.5 COS Coordinate System

Change Log

Version Cycle 34 May 2026

PROPINST-91445 Document COS FUV Lifetime Position Changes

Version Cycle 33 May 2025

Fixed the link to Table 11.1

Version Cycle 31 June 2023

Removed old PR link from Change Log.

Version Cycle 30 April 2022

PROPINST-91380 Document COS FUV Lifetime Position 6

Version Cycle 29 May 2021

Worked on comments from the COS team related to the changes for LP5.

Version Cycle 29 April 2021

PROPINST-91377 APT requirements for supporting COS FUV Lifetime Position 5
PROPINST-89772 Remove c1223 from Proposal Instructions (From Cycle 26)

Version Cycle 26 October 2018

PR.89179 Remove COS 1223 cenwave from user accessibility
11.5.2 COS Spectral Elements and Central Wavelengths
PR.89772 Remove c1223 from Proposal Instructions
11.5.2 COS Spectral Elements and Central Wavelengths

Initial Conversion from the HST Cycle 25 Phase II Proposal Instructions (Engineering) Version Cycle 25 (June 2018)

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11.5.2 COS Spectral Elements and Central Wavelengths

This article lists the combinations of spectral element and wavelength available for COS observations.

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