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

TL;DR

The ALICE instrument on New Horizons is a lightweight UV spectrograph designed to analyze atmospheres and surfaces of Pluto, Charon, and Kuiper Belt Objects through UV spectroscopy and surface reflectivity measurements.

Contribution

This paper details the design, calibration, and initial performance of ALICE, a novel lightweight UV spectrograph for planetary and Kuiper Belt object exploration.

Findings

Successful ground calibration of ALICE instrument.

Initial in-flight performance matches design specifications.

Detected atmospheric and surface features of Pluto and Kuiper Belt objects.

Abstract

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.