four thrusters to control attitude. Orientation of the spacecraft was determined by a star tracker, two sun sensors and two inertial measurement units. Orientation was controlled by firing the thrusters or using three reaction wheels. To perform the Mars orbital insertion maneuver, the spacecraft also included a LEROS 1B main engine rocket, providing of thrust by burning hydrazine fuel with nitrogen tetroxide (NTO) oxidizer. The spacecraft included a high-gain antenna to transceive data with the Deep Space Network over the x band. The radio transponder designed for the Cassini–Huygens mission was used as a cost-saving measure. It also included a two-way UHF radio frequency system to relay communications with Mars Polar Lander upon an expected landing on December 3, 1999. The space probe was powered with a 3-panel solar array, providing an average of at Mars. Deployed, the solar array measured in length. Power was stored in 12-cell, 16-amp-hour nickel-hydrogen batteries. The batteries were intended to be recharged when the solar array received sunlight and power the spacecraft as it passed into the shadow of Mars. When entering into orbit around Mars, the solar array was to be utilized in the aerobraking maneuver, to slow the spacecraft until a circular orbit was achieved. The design was largely adapted from guidelines from the Small Spacecraft Technology Initiative outlined in the book, Technology for Small Spacecraft. In an effort to simplify previous implementations of computers on spacecraft, Mars Climate Orbiter featured a single computer using an IBM RAD6000 processor utilizing a POWER1 ISA capable of 5, 10 or 20 MHz operation. Data storage was to be maintained on 128 MB of random-access memory (RAM) and 18 MB of flash memory. The flash memory was intended to be used for highly important data, including triplicate copies of the flight system software. Scientific instruments Pressure Modulated Infrared Radiometer (PMIRR) The Pressure Modulated Infrared Radiometer (PMIRR) uses narrow-band radiometric channels and two pressure modulation cells to measure atmospheric and surface emissions in the thermal infrared and a visible channel to measure dust particles and condensates in the atmosphere and on the surface at varying longitudes and seasons. Its principal investigator was Daniel McCleese at JPL/CALTECH. Similar objectives were later achieved with Mars Climate Sounder on board Mars Reconnaissance Orbiter. Its objectives: Map the three-dimensional and time-varying thermal structure of the atmosphere from the surface to 80 km altitude. Map the atmospheric dust loading and its