Alice (spacecraft instrument)

Alice is an ultraviolet imaging spectrometer for spacecraft, with one used on the New Horizons spacecraft, and another on the Rosetta spacecraft.[1] Alice is a small telescope with a spectrograph and a special detector with 32 pixels each with 1024 spectral channels detecting ultraviolet light.[2]

Infrographic of Alice data from its 2015 encounter with Pluto on New Horizons

Alice has an off-axis telescope which sends light to a Rowland-circle spectrograph, and the instrument has a field of view of 6 degrees.[3] It is designed to capture airglow and solar occultation at the same time, and has two inputs to allow this.[4]

Overview

Alice uses an array of potassium bromide and caesium iodide type of photocathodes. It detects in the extreme and far ultraviolet spectrum, from 700–2,050 Å (70–205 nm) wavelengths of light.[5][6]

Alice is intended, among its capabilities, to detect ultraviolet signatures of noble (aka inert) gases including helium, neon, argon, and krypton.[7] Alice should also be able to detect water, carbon monoxide, and carbon dioxide in the ultraviolet.[8]

ALICE was built and operated by the Southwest Research Institute for NASA's Jet Propulsion Laboratory.[9]

Naming

Alice is named after a character in The Honeymooners (1950s television show),[10] along with another New Horizons instrument, Ralph.

Alice on New Horizons

Alice installed on New Horizons spacecraft

In August 2018, NASA confirmed, based on results by Alice on the New Horizons spacecraft, the detection of a "hydrogen wall" at the outer edges of the Solar System that was first detected in 1992 by the two Voyager spacecraft which have detected a surplus of ultraviolet light determined to be coming from hydrogen.[11][12]

The New Horizons version of Alice uses an average power of 4.4 watts and weighs 4.5 kg (9.9 pounds).[13]

Examples
Name	Wavelength Bandpass	Aperture(s)
Human eye	400–700 nm (approx.)[14]	0.6 cm[15]
LORRI	350 – 850 nm	20.8 cm
Alice	70-205 nm[16][17]	(two; 40 x 40 mm^2 1 mm [18]

Alice on Rosetta

On Rosetta, a mission to a comet, Alice performed ultraviolet spectroscopy to search and quantify the noble gas content in the comet nucleus.[19][20]

On Rosetta it is a 3.1 kg (6.8 lb) instrument which uses 2.9 watts.[21][22]

See also

• UVS (Juno) (ultraviolet imaging spectrometer on Juno Jupiter orbiter)
• Ultraviolet–visible spectroscopy
• List of New Horizons topics

References

1. "The New Horizons Alice UV Spectrometer". www.boulder.swri.edu. Retrieved 2018-10-20.
2. "New Horizons". pluto.jhuapl.edu. Archived from the original on 2018-05-01. Retrieved 2018-10-20.
3. "ALICE: The ultraviolet imaging spectrograph aboard the New Horizons Pluto mission spacecraft". ResearchGate. Retrieved 2018-12-19.
4. "ALICE: The ultraviolet imaging spectrograph aboard the New Horizons Pluto mission spacecraft". ResearchGate. Retrieved 2018-12-19.
5. Stern, S. A.; Slater, D. C.; Scherrer, J.; Stone, J.; Versteeg, M.; et al. (February 2007). "Alice: The Rosetta Ultraviolet Imaging Spectrograph". Space Science Reviews. 128 (1–4): 507–527. arXiv:astro-ph/0603585. Bibcode:2007SSRv..128..507S. doi:10.1007/s11214-006-9035-8.
6. Stern, S. A.; Slater, D. C.; Gibson, W.; Scherrer, J.; A'Hearn, M.; et al. (1998). "Alice—An Ultraviolet Imaging Spectrometer for the Rosetta Orbiter". Advances in Space Research. 21 (11): 1517–1525. Bibcode:1998AdSpR..21.1517S. doi:10.1016/S0273-1177(97)00944-7.
7. "ALICE Overview | Rosetta". rosetta.jpl.nasa.gov. Retrieved 2018-10-20.
8. "ALICE Overview | Rosetta". rosetta.jpl.nasa.gov. Retrieved 2018-10-20.
9. "Rosetta-Alice spectrograph to begin first-ever close up ultraviolet studies of comet surface and atmosphere". Southwest Research Institute. 10 June 2014. Retrieved 28 December 2016.
10. "The Museum of Broadcast Communications - Encyclopedia of Television - Honeymooners, The". www.museum.tv. Archived from the original on 2014-10-06. Retrieved 2018-12-31.
11. Gladstone, G. Randall; et al. (7 August 2018). "The Lyman‐α Sky Background as Observed by New Horizons". Geophysical Research Letters. 45 (16): 8022–8028. arXiv:1808.00400. Bibcode:2018GeoRL..45.8022G. doi:10.1029/2018GL078808.
12. Letzter, Rafi (9 August 2018). "NASA Spotted a Vast, Glowing 'Hydrogen Wall' at the Edge of Our Solar System". Live Science. Retrieved 10 August 2018.
13. "New Horizons". pluto.jhuapl.edu. Archived from the original on 2018-05-01. Retrieved 2018-10-20.
14. "What Is the Visible Light Spectrum?". ThoughtCo. Retrieved 2018-11-09.
15. "How to Calculate the F-stop of the Human Eye". Popular Photography. Retrieved 2018-11-09.
16. Stern, S. A.; Slater, D. C.; Scherrer, J.; Stone, J.; Versteeg, M.; et al. (February 2007). "Alice: The Rosetta Ultraviolet Imaging Spectrograph". Space Science Reviews. 128 (1–4): 507–527. arXiv:astro-ph/0603585. Bibcode:2007SSRv..128..507S. doi:10.1007/s11214-006-9035-8.
17. Stern, S. A.; Slater, D. C.; Gibson, W.; Scherrer, J.; A'Hearn, M.; et al. (1998). "Alice—An Ultraviolet Imaging Spectrometer for the Rosetta Orbiter". Advances in Space Research. 21 (11): 1517–1525. Bibcode:1998AdSpR..21.1517S. doi:10.1016/S0273-1177(97)00944-7.
18. 3.1
19. Stern, S. A.; Slater, D. C.; Scherrer, J.; Stone, J.; Versteeg, M.; et al. (February 2007). "Alice: The Rosetta Ultraviolet Imaging Spectrograph". Space Science Reviews. 128 (1–4): 507–527. arXiv:astro-ph/0603585. Bibcode:2007SSRv..128..507S. doi:10.1007/s11214-006-9035-8.
20. Stern, S. A.; Slater, D. C.; Gibson, W.; Scherrer, J.; A'Hearn, M.; et al. (1998). "Alice—An Ultraviolet Imaging Spectrometer for the Rosetta Orbiter". Advances in Space Research. 21 (11): 1517–1525. Bibcode:1998AdSpR..21.1517S. doi:10.1016/S0273-1177(97)00944-7.
21. Stern, S. A.; Slater, D. C.; Scherrer, J.; Stone, J.; Versteeg, M.; et al. (February 2007). "Alice: The Rosetta Ultraviolet Imaging Spectrograph". Space Science Reviews. 128 (1–4): 507–527. arXiv:astro-ph/0603585. Bibcode:2007SSRv..128..507S. doi:10.1007/s11214-006-9035-8.
22. Stern, S. A.; Slater, D. C.; Gibson, W.; Scherrer, J.; A'Hearn, M.; et al. (1998). "Alice—An Ultraviolet Imaging Spectrometer for the Rosetta Orbiter". Advances in Space Research. 21 (11): 1517–1525. Bibcode:1998AdSpR..21.1517S. doi:10.1016/S0273-1177(97)00944-7.