The High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) is a powerful camera system designed to provide detailed images of Mars. The HiRISE camera features a 0.5-meter primary mirror, an effective focal length of 12 meters, and a focal plane system capable of acquiring images containing up to 28 gigabits of data in as little as 6 seconds. During the 2-year Primary Science Phase (PSP) starting in November 2006, HiRISE will cover approximately 1% of the Martian surface with images of 0.25 to 1.3 meters per pixel, including color data for 20% of the potential field of view. A key priority is to acquire approximately 1000 stereo pairs to enable topographic measurements with better than 25 cm vertical precision. The camera uses 14 CCD detectors, each with 2 output channels, and supports multiple choices for pixel binning and the number of Time Delay and Integration (TDI) lines. HiRISE will support Mars exploration by locating and characterizing past, present, and future landing sites, unsuccessful landing sites, and rover traverses. It will also investigate various geological and atmospheric processes, including cratering, volcanism, tectonism, hydrology, sedimentary processes, stratigraphy, aeolian processes, mass wasting, landscape evolution, seasonal processes, climate change, spectrophotometry, glacial and periglacial processes, polar geology, and regolith properties. An Internet Web site (HiWeb) allows users to suggest HiRISE targets and access HiRISE data products. The instrument's performance, calibration, and science planning are detailed, highlighting its capabilities and the scientific contributions it will make to Mars exploration.The High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) is a powerful camera system designed to provide detailed images of Mars. The HiRISE camera features a 0.5-meter primary mirror, an effective focal length of 12 meters, and a focal plane system capable of acquiring images containing up to 28 gigabits of data in as little as 6 seconds. During the 2-year Primary Science Phase (PSP) starting in November 2006, HiRISE will cover approximately 1% of the Martian surface with images of 0.25 to 1.3 meters per pixel, including color data for 20% of the potential field of view. A key priority is to acquire approximately 1000 stereo pairs to enable topographic measurements with better than 25 cm vertical precision. The camera uses 14 CCD detectors, each with 2 output channels, and supports multiple choices for pixel binning and the number of Time Delay and Integration (TDI) lines. HiRISE will support Mars exploration by locating and characterizing past, present, and future landing sites, unsuccessful landing sites, and rover traverses. It will also investigate various geological and atmospheric processes, including cratering, volcanism, tectonism, hydrology, sedimentary processes, stratigraphy, aeolian processes, mass wasting, landscape evolution, seasonal processes, climate change, spectrophotometry, glacial and periglacial processes, polar geology, and regolith properties. An Internet Web site (HiWeb) allows users to suggest HiRISE targets and access HiRISE data products. The instrument's performance, calibration, and science planning are detailed, highlighting its capabilities and the scientific contributions it will make to Mars exploration.