ALICE: The Ultraviolet Imaging Spectrograph aboard the New Horizons Pluto-Kuiper Belt Mission

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 520-1870 angstroms spectral passband, a spectral point spread function of 3-6 angstroms 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. In what follows, we describe the instrument in greater detail, including descriptions of its ground calibration and initial in flight performance.Comment: 24 pages, 29 figures, 2 tables; To appear in a special volume of Space Science Reviews on the New Horizons missio

20 cm Sealed Tube Photon Counting Detectors with Novel Microchannel Plates for Imaging and Timing Applications

AbstractAs part of a collaborative program between University of California, Berkeley, the Argonne National Laboratory, University of Chicago, and several commercial companies, a 20cm square sealed tube microchannel plate detector scheme with a proximity focused bialkali photocathode is being developed. Sealed tube microchannel plate deviceshave good imaging and timing characteristics, but large areas have been previously unavailable. We have madeb considerable progress in fabricating large size microchannel plates. A key feature is the novel implementation of low cost microchannel plates using borosilicate micro-capillary arrays with hollow core tubes. The resistive and secondary electron emissive surfaces are then applied by atomic layer deposition, eliminating the wet etch and thermal reduction processes for normal glass microchannel plates. Initial results with 33mm format microchannel plates for gain, pulse width, imaging performance and lifetime are comparable to conventional MCPs. Large 20cm square microchannel plate prototypes with 20μm and 40μm pores have been fabricated and initial tests show operational gain. Design and fabrication of a 20cm sealed tube assembly is well advanced and comprises a borosilicate entrance window, a proximity focused bialkali photocathode, a pair of microchannel plates and a stripline readout anode. The design employs a brazed ceramic walled enclosure and a transfer tube type photocathode with an indium seal. We have adopted a baseline bialkali photocathode to match the anticipated input spectrum, and have made a number of test cathodes with >20% peak quantum efficiency on borofloat-33 window material. Stripline anodes are also being developed which will give less than 1mm spatial resolution using custom ASIC amplification and timing electronics