Alice (spacecraft instrument)

Alice uses an array of potassium bromide and caesium iodide type of photocathodes. It detects in the extreme and far ultraviolet spectrum, from {{convert|700|-|2050|Å|nm|abbr=on}} wavelengths of light, with a spectral resolution of {{convert|8|-|12|Å|nm|abbr=on}} and a spatial resolution of {{convert|500|m|ft|abbr=off}} per {{convert|50|km|miles|abbr=on}} of altitude.{{cite journal |title=Alice: The Rosetta Ultraviolet Imaging Spectrograph |journal=Space Science Reviews |first1=S. A. |last1=Stern |first2=D. C. |last2=Slater |first3=J. |last3=Scherrer |first4=J. |last4=Stone |first5=M. |last5=Versteeg |first6=M. F. |last6=A'Hearn |first7=J. L. |last7=Bertaux |first8=P. D. |last8=Feldman |first9=M. C. |last9=Festou |first10=Joel Wm. |last10=Parker |first11=O. H. W. |last11=Siegmund |display-authors=5 |volume=128 |issue=1–4 |pages=507–527 |date=February 2007 |doi=10.1007/s11214-006-9035-8 |bibcode=2007SSRv..128..507S |arxiv=astro-ph/0603585|s2cid=44273197 }}{{cite journal |title=Alice—An Ultraviolet Imaging Spectrometer for the Rosetta Orbiter |journal=Advances in Space Research |first1=S. A. |last1=Stern |first2=D. C. |last2=Slater |first3=W. |last3=Gibson |first4=J. |last4=Scherrer |first5=M. |last5=A'Hearn |first6=J. L. |last6=Bertaux |first7=P. D. |last7=Feldman |first8=M. C. |last8=Festou |display-authors=5 |volume=21 |issue=11 |pages=1517–1525 |year=1998 |doi=10.1016/S0273-1177(97)00944-7 |bibcode=1998AdSpR..21.1517S|doi-access=free }}

Alice is intended, among its capabilities, to detect ultraviolet signatures of noble (aka inert) gases including helium, neon, argon, and krypton.{{Cite web|url=https://rosetta.jpl.nasa.gov/us-instruments/alice-overview|archive-url=https://web.archive.org/web/20130218113030/http://rosetta.jpl.nasa.gov/us-instruments/alice-overview|url-status=dead|archive-date=2013-02-18|title=ALICE Overview {{!}} Rosetta|website=rosetta.jpl.nasa.gov|language=en|access-date=2018-10-20}} Alice should also be able to detect water, carbon monoxide, and carbon dioxide in the ultraviolet. Although the instrument was designed to study Pluto's atmosphere, ALICE will also be tasked with studying Pluto's moon Charon, in addition to various Kuiper-belt objects.

ALICE was built and operated by the Southwest Research Institute for NASA's Jet Propulsion Laboratory.{{cite web |url=http://www.swri.org/9what/releases/2014/rosetta-alice.htm |title=Rosetta-Alice spectrograph to begin first-ever close up ultraviolet studies of comet surface and atmosphere |publisher=Southwest Research Institute |date=10 June 2014 |access-date=28 December 2016}} The instrument is powered using a radiation hardened version of an Intel 8052 micro-processor. The instrument uses 32KB of programmable read only memory (PROM), 128 KB of EEPROM, and 32KB of SRAM. The command and data handling electronics are contained across four circuit boards which sit behind the detectors.{{Cite book |last=Stern |first=Alan |title=ALICE: The Ultraviolet Imaging Spectrograph Aboard the New Horizons Pluto–Kuiper Belt Mission |publisher=Dordrecht: Springer Netherlands |year=2008 |pages=163}}

ALICE operates in two separate data modes; Pixel List mode (PLM) and Histogram mode (HM). In Pixel List mode, the number of photons/second are recorded. In Histogram mode, the sensor array collects data/photons for a defined period of time. This data is then read as a 2D image. Furthermore, whilst the image is being read from the first memory bank, a second exposure can be started using the secondary memory bank. An advantage of utilising two different data modes is that the method of data collection can be tailored to the scientific goals. PLM provides time resolution, where as HM consistently requires same amount of memory, regardless of exposure length.

Alice is not an acronym. The name was chosen by principal investigator Alan Stern for personal reasons.

File:Alice ultraviolet imaging spectrometer on New Horizons.jpeg

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.{{cite journal |author=Gladstone, G. Randall|display-authors=et al |title=The Lyman‐α Sky Background as Observed by New Horizons

|date=7 August 2018 |journal=Geophysical Research Letters |volume=45 |issue=16 |pages=8022–8028 |doi=10.1029/2018GL078808 |arxiv=1808.00400 |bibcode=2018GeoRL..45.8022G |s2cid=119395450 }}{{cite web |last=Letzter |first=Rafi |title=NASA Spotted a Vast, Glowing 'Hydrogen Wall' at the Edge of Our Solar System

|url=https://www.livescience.com/63297-hydrogen-wall-glowing-interstellar-space.html |date=9 August 2018 |work=Live Science |access-date=10 August 2018 }}

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

{{Clear}}

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

On Rosetta it is a {{convert|3.1|kg|abbr=on}} instrument which uses 2.9 watts.

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

{{Reflist}}

{{NH1}}

{{Rosetta mission}}

{{Satellite and spacecraft instruments}}

Category:Spacecraft instruments

Category:New Horizons

Category:Rosetta mission

Category:Spectrometers