Compact Reconnaissance Imaging Spectrometer for Mars

Compact Reconnaissance Imaging Spectrometer for Mars
Name	Compact Reconnaissance Imaging Spectrometer for Mars
Acronym	CRISM
Mission	Mars Reconnaissance Orbiter
Operator	JPL / Lockheed Martin
Launch	2005
Instrument type	Imaging spectrometer
Spectral range	0.36–3.92 μm
Resolution	~18–36 m/pixel (multispectral), ~18–19 nm spectral
Status	Operational (intermittent)

Compact Reconnaissance Imaging Spectrometer for Mars is a visible to shortwave infrared imaging spectrometer carried by the Mars Reconnaissance Orbiter that mapped mineralogy across Mars to identify aqueous alteration minerals, stratigraphy, and surface processes. Developed by teams at Brown University, Malin Space Science Systems, and Arizona State University in collaboration with the Jet Propulsion Laboratory, CRISM combined high spectral resolution with targeted high spatial resolution sampling to guide landing site selection, support rover operations, and test hypotheses about past Mars climate and habitability.

Overview

CRISM was built for the Mars Reconnaissance Orbiter mission managed by NASA and served as a key payload alongside instruments such as the High Resolution Imaging Science Experiment and the Mars Climate Sounder. The instrument measured reflected sunlight from the Martian surface and atmosphere across hundreds of narrow spectral channels to detect diagnostic absorption features of minerals related to aqueous alteration, including phyllosilicates, sulfates, carbonates, and hydrated salts. CRISM operations involved coordination with teams at JPL, Brown University, and science investigators from institutions including Cornell University, University of Arizona, and University of Colorado.

Instrument Design and Specifications

CRISM employed an imaging spectrometer design using a two-channel system: a multispectral mapping mode and a hyperspectral targeted mode. The optical system incorporated monocromatic dispersive elements, focal plane arrays, and cryogenic cooling developed with support from Lockheed Martin and detector specialists tied to programs at Ball Aerospace and Teledyne. Spectral coverage spanned roughly 0.36–3.92 μm with spectral sampling sufficient to resolve overtone and combination bands of OH, H2O, CO3, and SO4-bearing minerals; the instrument provided ~544 spectral bands in targeted observations and fewer bands in mapping operations. Spatial sampling varied from tens of meters per pixel in hyperspectral "FRT" observations to several hundred meters in global multispectral "MSP" mapping, enabling cross-comparison with datasets from Mars Global Surveyor and Mars Odyssey.

Scientific Objectives and Capabilities

CRISM's primary objectives included detection and mapping of alteration minerals indicative of past aqueous environments, characterization of sedimentary and volcanic layering, investigation of polar and regolith hydration, and identification of potential resource-bearing deposits for future missions. The instrument could discriminate between mineral classes such as clay minerals (e.g., smectite), sulfate minerals (e.g., gypsum), and carbonate minerals (e.g., calcite) by measuring diagnostic absorption positions and shapes. CRISM observations supported synergistic science with the Mars Exploration Rover missions and the Mars Science Laboratory by providing regional context for landing sites like Gale Crater and for features investigated at local scales by Opportunity and Spirit.

Data Products and Processing

CRISM data products included calibrated radiance, reflectance (I/F), surface mineralogical maps, summary parameter products highlighting spectral features, and browse images for mission planning. Processing pipelines at JPL and partner institutions applied dark current subtraction, spectral smile correction, photometric corrections referencing solar analogs, and atmospheric removal using radiative transfer models adapted from tools used for Hubble Space Telescope solar system spectroscopy and terrestrial hyperspectral missions. Higher-level products such as summary parameter maps and mineralogical interpretation layers were disseminated to investigators and archives maintained by NASA data centers and science teams at Brown University.

Mission Deployments and Operations

CRISM was deployed on the Mars Reconnaissance Orbiter launched in 2005 and entered the Mars science orbit in 2006, conducting targeted campaigns during both primary and extended missions. Operations required planning within the constraints of the orbiter's ground track, solar illumination, and onboard data volume budgets; science teams used sequences of targeted observations (FRT, HRL, MSP modes) to balance global coverage and high-resolution sampling. Coordination with instruments such as the Context Camera and the Shallow Radar instrument enhanced stratigraphic interpretation and subsurface context. CRISM operations adapted to spacecraft events, including reaction wheel issues and orbit maintenance, with rehabilitation and recalibration campaigns conducted by teams at JPL and partner universities.

Key Discoveries and Scientific Impact

CRISM produced pivotal discoveries that reshaped understanding of Mars aqueous history: widespread detection of phyllosilicates implying early neutral-to-alkaline alteration environments, layered sulfate deposits consistent with evaporitic processes, localized carbonate outcrops suggesting CO2 sequestration potential, and detection of hydrated salts linked to modern brine activity at recurring slope lineae-like sites. These findings influenced hypotheses about Mars paleoclimate, informed selection of landing sites such as for the Mars Science Laboratory and Mars 2020 missions, and guided laboratory analog studies at institutions including Smithsonian Institution and US Geological Survey. CRISM datasets underpinned hundreds of peer-reviewed studies across journals tied to the American Geophysical Union and Nature Publishing Group.

Calibration, Limitations, and Future Developments

Calibration efforts for CRISM addressed instrument artifacts, spectral smile, detector nonlinearity, and atmospheric correction challenges; teams at JPL, Brown University, and detector vendors performed inflight calibration using solar and lunar analog observations and cross-calibration with instruments on Mars Global Surveyor and Mars Odyssey. Limitations included data volume constraints that limited global hyperspectral coverage, aging detector performance, and difficulty separating surface from atmospheric spectral components in dusty or cloudy conditions. Future developments driven by CRISM heritage include higher-throughput hyperspectral imagers proposed for missions by European Space Agency, Roscosmos, Indian Space Research Organisation, and commercial operators, as well as rover-based spectrometers on missions such as Perseverance and proposed sample return campaigns that build on CRISM mineralogical maps to ground-truth regional interpretations.

Category:Instruments of the Mars Reconnaissance Orbiter