An Ultraviolet Spectrometer for the Rosetta Orbiter

ALICE Instrument, Optical Details

The ALICE optical design consists of:

40 x 40 mm² off-axis parabolic primary
Rowland circle design for the spectrograph
Holographic grating by Y. Jobin
SiC coated optics on Ni polished surface on Al substrate

Optical Performance Summary

Bandpass 700 - 2050 Angstroms

Spectral Resolution 5.6 Angstroms, point source
12.5 Angstroms, extended source at 700 Angstroms
9.8 Angstroms, extended source at 2050 Angstroms

Spatial Resolution 0.1 x 6.0 degree²
(70 x 420 m² at 40 km)

Active FOV 0.1 x 6.0 degree²

Nominal Effective Area 0.03 (1900 Angstroms) - 0.53 cm² (1150 Angstroms)

Nominal Sensitivity 0.5 (1900 Angstroms) - 7.8 (1150 Angstroms) c s^-1 R^-1

Detector Dark Current Rate 3 - 7 count s^-1

Optical Performance Summary
Bandpass	700 - 2050 Angstroms
Spectral Resolution	5.6 Angstroms, point source 12.5 Angstroms, extended source at 700 Angstroms 9.8 Angstroms, extended source at 2050 Angstroms
Spatial Resolution	0.1 x 6.0 degree² (70 x 420 m² at 40 km)
Active FOV	0.1 x 6.0 degree²
Nominal Effective Area	0.03 (1900 Angstroms) - 0.53 cm² (1150 Angstroms)
Nominal Sensitivity	0.5 (1900 Angstroms) - 7.8 (1150 Angstroms) c s^-1 R^-1
Detector Dark Current Rate	3 - 7 count s^-1

Resolving Power Graph

Spectral Resolution vs Slit Width

Predicted resolving power of ALICE for point sources and extended sources (0.1 x 6 deg.²) as a function of wavelength

Point Source Spot Diagrams

ALICE point source spot diagrams at 700, 1300 and 2000 Angstroms. Pixel size for the (512 x 32)-pixel format is 0.068mm in X-dimension by 0.625 mm in Y-dimension.