PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = " 2006-12-27 SOC:Carcich Initial version; " RECORD_TYPE = STREAM OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "NH" INSTRUMENT_ID = "ALICE" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "ALICE UV IMAGER" INSTRUMENT_TYPE = "SPECTROGRAPH" INSTRUMENT_DESC = " ######################################################################## ######################################################################## REQUIRED READING: - Stern et al. (2007) [STERNETAL2007] ######################################################################## ######################################################################## The ALICE description is adapted from Slater et al. (2007) [SLATERETAL2007] and Stern et al. (2005) [STERNETAL2005]. INSTRUMENT OVERVIEW ======== The New Horizons ALICE instrument is a lightweight (4.4 kg), low-power (4.4 Watt) imaging spectrograph aboard the New Horizons mission to Pluto/Charon and the Kuiper Belt. Its primary job is to determine the relative abundances of various species in Pluto's atmosphere. ALICE will also be used to search for an atmosphere around Pluto's moon, Charon, as well as the Kuiper Belt Objects (KBOs) that New Horizons hopes to fly by after Pluto-Charon, and it will make UV surface reflectivity measurements of all of these bodies as well. The instrument incorporates an off-axis telescope feeding a Rowland-circle spectrograph with a 520-1870A spectral passband, a spectral point spread function of 3-6A FWHM, and an instantaneous spatial field-of-view that is 6 degrees long. Different input apertures that feed the telescope allow for both airglow and solar occultation observations during the mission. The focal plane detector is an imaging microchannel plate (MCP) double delay-line detector with dual solar-blind opaque photocathodes (KBr and CsI) and a focal surface that matches the instrument's 15-cm diameter Rowland-circle. SPECIFICATIONS -------- NAME: ALICE DESCRIPTION: Ultraviolet Mapping Spectrograph PRINCIPAL INVESTIGATOR: Alan Stern, SwRI WAVELENGTH RANGE: 52 - 180 nm FIELD OF VIEW: 1.7 x 70 mRad (Note 1); 35 x 35 mRad (Note 2) ANGULAR RESOLUTION: 1.7 x 5.2 mRad WAVELENGTH RESOLUTION: 0.183 nm Note 1: Slit Note 2: Solar occultation aperture DESCRIPTION -------- This ALICE is a lightweight (4.4 kg), low-power (4.4 W), ultraviolet spectrograph based on the ALICE instrument now in flight aboard the European Space Agency's Rosetta spacecraft. Its primary job will be to detect a variety of important atomic and molecular species in Pluto's atmosphere, and to determine their relative abundances so that a complete picture of Pluto's atmospheric composition can be determined for the first time. ALICE will also be used to search for an atmosphere around Pluto's moon, Charon, as well as the Kuiper Belt Objects (KBOs) New Horizons hopes to fly by after Pluto-Charon. Light can enter the telescope section through either a 40mm x 40mm entrance aperture (i.e. the airglow channel) or a stopped-down 1-mm diameter entrance aperture and flat relay mirror (i.e. the SOC) and is collected and focused by an off-axis paraboloidal (OAP) primary mirror onto the spectrograph entrance slit. The OAP has a 120 mm focal length. Scientific Objectives ======== Upper atmospheric temperature and pressure profiles of Pluto Temperature and vertical temperature gradient should be measured to ~10% at a vertical resolution of ~100 km for atmospheric densities greater than ~109 cm-3. Search for atmospheric haze at a vertical resolution <5 km Mole fractions of N2, CO, CH4 and Ar in Pluto's upper atmosphere. Atmospheric escape rate from Pluto Minor atmospheric species at Pluto Search for an atmosphere of Charon Constrain escape rate from upper atmospheric structure Calibration ======== See Stern et al. (2007) for details. Operational Considerations ======== The New Horizons ALICE UV spectrometer was successfully launched on 19 January 2006 and is operating normally in space. All in flight performance tests to date have shown performance within specification; the pointing and AGC sensitivity tests completed in September 2006 are in analysis, and the initial results of these tests indicate nominal performance. The primary remaining tests to be performed will be testing of the solar occultation aperture after it is opened near the end of 2006, and instrument mutual noise susceptibility testing in the spring of 2007. Detectors ======== Summary is above; see Stern et al. (2007) for details. Electronics ======== Major electronic subsystems are - Low-Voltage Power Supply Electronics. - Command-and-Data-Handling Electronics. - Decontamination Heaters. - High Voltage Power Supplies. See Stern et al. (2007) for details. Optics ======== Summary information is above; see Stern et al. (2007) for details. Operational Modes ======== Alice has two separate entrance apertures that feed light to the telescope section of the instrument: an 'airglow' aperture, which allows measurement of emissions from atmospheric constituents, and an 'occultation' aperture, when either the Sun or a bright star is viewed through the atmosphere producing absorption by the atmospheric constituents. The Alice occultation mode will be used just after New Horizons passes behind Pluto and looks back at the Sun through Pluto's atmosphere. P-ALICE has two detector data collection modes described in detail below: (i) pixel list mode; and (ii) histogram mode. The P-ALICE flight software controls both of these modes. Data is collected in a dual port acquisition memory that consists of two separate 32kx16-bit memory channels. In Pixel List Mode (PLM) a continuous time series of photon counts is generated with a series of interspersed time hacks at a programmable interval, which can be as short as 4 msec. In Histogram Imaging Mode (HIM) the detector integrates for a specified period and then reads out its entire 2-D array as an image. In HIM, each memory location thus represents a pixel location in the detector 2-D 1024x32 array. See Stern et al. (2007) for further details. Measured Parameters ======== Time and pixel location of photon count events (Pixel List Mode) OR Photon counts at each pixel location (Histogram Imaging Mode) " END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "STERNETAL2007" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "SLATERETAL2005" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "STERNETAL1995" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "SLATERETAL2001" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "STERNETAL2005" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "SIEGMUNDETAL1992" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "SIEGMUND2000" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "DANZMANNETAL1988" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END