PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2006-06-07, R. Sharrow, initial; 2006-12-20, S. Slavney, revised" RECORD_TYPE = STREAM OBJECT = INSTRUMENT_HOST INSTRUMENT_HOST_ID = "MRO" OBJECT = INSTRUMENT_HOST_INFORMATION INSTRUMENT_HOST_NAME = "MARS RECONNAISSANCE ORBITER" INSTRUMENT_HOST_TYPE = "SPACECRAFT" INSTRUMENT_HOST_DESC = " Instrument Host Overview ======================== Mars Reconnaissance Orbiter Spacecraft -------------------------------------- Mars Reconnaissance Orbiter uses a spacecraft design provided by Lockheed Martin Space Systems that is smarter, more reliable, more agile, and more productive than any previous Mars orbiter. It is the first spacecraft designed from the ground up for aerobraking, a rigorous phase of the mission where the orbiter uses the friction of the martian atmosphere to slow down in order to settle into its final orbit around Mars. When fully assembled and fueled, the spacecraft had to weigh less than 2,180 kilograms (4,806 pounds) so that the Atlas V launch vehicle could lift it into the proper orbit. All subsystems and instruments on board (the so-called 'dry mass') weighed less than 1,031 kilograms (2,273 pounds) to allow room for 1,149 kilograms (2,533 pounds) of propellant for trajectory correction maneuvers that kept the spacecraft on target during the cruise to Mars and for burns that helped capture the spacecraft into orbit around Mars. Spacecraft Configurations ------------------------- During its five-year mission, the spacecraft needed to operate in four distinct mission phases. Launch: During launch, the spacecraft had to fit within the nose cone, or payload fairing, of the launch vehicle, so the large parts like the high-gain antenna and the solar arrays were designed to be folded up. As soon as the launch vehicle placed the spacecraft on a course to leave earth orbit for its journey to Mars, it disconnected itself from the spacecraft. Cruise: As soon as the spacecraft was clear of the launch vehicle, the orbiter deployed its solar arrays to begin producing power. The high-gain antenna was also be deployed at this point. The high-gain antenna moved to track the Earth, while the solar panels remained fixed. Mars Orbit Insertion and Aerobraking: The Mars orbit insertion and aerobraking configuration looked very much like the cruise configuration, except that the high-gain antenna was moved to a position that balanced the solar arrays as it flew through the upper atmosphere of Mars. The heaviest part of the spacecraft (the propellant tank) also made the spacecraft very stable. Due to the large area (37.7 square meters or 405.8 square feet) of the spacecraft in this configuration, each pass through the martian atmosphere during aerobraking caused significant slowing, thus reducing the size of the orbit. Friction from the atmosphere had the additional effect of heating up the spacecraft, so components were designed to withstand this heating. The flight team could further control the heating by changing how deeply the spacecraft dipped into the atmosphere on each orbit. Science Operations: During the primary science phase, the orbiter's job was to point its science instruments at Mars to collect images and other data from targets on the surface of Mars, while ensuring that the high-gain antenna and solar arrays were continuously tracking the Earth and the Sun, respectively. The orbiter typically kept its science instruments pointed to nadir (looking straight down at the surface). A few times per day, and for about fifteen minutes each time, the orbiter pointed side- to-side in order to capture high-priority science targets that did not fall directly beneath the spacecraft. The spacecraft could point off-nadir up to 30 degrees. Major Spacecraft Components --------------------------- Science Payload Instruments: To fulfill the mission science objectives, seven scientific investigations teams were selected by NASA. Four teams (MARCI, MCS, HiRISE, and CRISM) were led by Principal Investigators (PI). Each PI lead team was responsible for the provision and operation of a scientific instrument and the analysis of its data. The PI lead investigations were: Mars Color Imager (MARCI); Mars Climate Sounder, (MCS); High Resolution Imaging Science Experiment, (HiRISE); and Compact Reconnaissance Imaging Spectrometer for Mars, (CRISM). In addition to the PI lead teams, there were two investigation teams that made use of facility instruments. The facility instruments were Context Imager (CTX) and Shallow (Subsurface) Radar (SHARAD). The MARCI PI and Science Team also acted as Team Leader (TL) and Team Members for the CTX facility instrument. The Italian Space Agency (ASI) provided a second facility instrument, SHARAD, for flight on MRO. ASI and NASA both selected members of the SHARAD investigation team with ASI appointing the Team Leader and NASA appointing the Deputy Team Leader. In addition to the instrument investigations, Gravity Science and Atmospheric Structure Facility Investigation Teams used data from the spacecraft telecommunications and accelerometers, respectively, to conduct scientific investigations. The science instruments are summarized below. Instrument: CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) Type: High-Resolution Imaging Spectrometer Measurements: Hyper-spectral Image Cubes, 514 spectral bands, 0.4-4 microns, 7 nm resolution, from 300km; 20 m/pixel, 11 km swath. Science Goals: Regional & local surface composition and morphology. Key Attributes: Moderately high spectral & spatial resolution, targeted and regional survey, very high data rate. Principal Investigator: Scott Murchie, Johns Hopkins University Applied Physics Lab. Instrument: CTX (Context Imager) Type: Mono-chromatic Context Camera Measurements: Panchromatic (minus blue)Images from 300km altitude; 30km swath & 6m/pixel context imaging for HiRISE/CRISM & MRO science. Science Goals: Regional stratigraphy and morphology. Key Attributes: Moderately high resolution with coverage, targeted & regional survey; high data rate. Team Leader: Michael Malin, Malin Space Science Systems (MSSS). Instrument: HiRISE (High Resolution Imaging Science Experiment) Type: High-Resolution Camera (0.5 m aperture) Measurements: Color images, stereo by site revisit, from 300km; < 1m/pixel (ground sampling @ 0.3 m/pixel), 6 km swath in red (broadband), 1.2km swath in blue-green & NIR. Science Goals: Stratigraphy, geologic processes and morphology. Key Attributes: Very high resolution targeted imaging, very high data rate. Principal Investigator: Alfred McEwen, University of Arizona. Instrument: MARCI (Mars Color Imager) Type: Wide-Angle Color Imager Measurements: Coverage of atmospheric clouds, hazes and ozone, and surface albedo in 7 color bands (0.28-0.8 micrometers) (2 UV, 5 Visible). Science Goals: Global weather and surface change. Key Attributes: Daily global coverage daily global mapping, continuous operations dayside; moderate data rate. Principal Investigator: Michael Malin, Malin Space Science Systems (MSSS). Instrument: MCS Type: Atmospheric Sounder Measurements: Atmospheric profiles of water, dust, co2 & temperature, polar radiation balance, 0-80km vertical coverage, vertical resolution ~5km. Science Goals: Atmospheric structure, transport and polar processes. Key Attributes: Global limb sounding; daily, global limb & on-planet mapping; continuous operations day and night; low data rate. Principal Investigator: Daniel J. McCleese, Jet Propulsion Lab (JPL). Instrument: SHARAD Type: Shallow Subsurface Radar Measurements: Ground penetrating radar; transmit split band at 20mhz <1km; 10-20 m vertical resolution 1km x 5km. Science Goals: Regional near-surface ground structure. Key Attributes: Shallow sounding; regional profiling; high data rate. Team Leader: Roberto Seu, University of Rome, Italy. Deputy Team Leader: Roger Phillips, Washington University, St. Louis. Engineering Instruments: Mars Reconnaissance Orbiter carried three instruments that will assist in spacecraft navigation and communications. 1. Electra UHF Communications and Navigation Package: Electra allowed the spacecraft to act as a communications relay between the Earth and landed crafts on Mars that may not have sufficient radio power to communicate directly with Earth by themselves. 2. Optical Navigation Camera: This camera was being tested for improved navigation capability for future missions. Similar cameras placed on orbiters of the future would be able to serve as high-precision interplanetary 'eyes' to guide incoming spacecraft as they near Mars. 3. Ka-band Telecommunications Experiment Package: Mars Reconnaissance Orbiter tested the use of a radio frequency called Ka-band to demonstrate the potential for greater performance in communications using significantly less power. Structures: The structures subsystem is the skeleton around which the spacecraft was assembled. It supported and protected the other engineering subsystems and the science instruments. It was strong enough to survive launch, when the forces can exceed 5 g's. Extremely lightweight but strong materials were used to achieve this strength, including titanium, carbon composites, and aluminum honeycomb. Mechanisms: There were three main mechanisms on board Mars Reconnaissance Orbiter: * one that allowed the high-gain antenna to move in order to point at earth * two that allowed the solar arrays to move to point at the sun Each of these mechanisms, called gimbals, moved about two axes in much the same way that your wrist allows your hand to move in two axes: left/right and up/down. As the spacecraft traveled around Mars each orbit, these gimbals allowed both solar arrays to be always pointed toward the sun, while the high-gain antenna could simultaneously always be pointed at earth. Telecommunications System: The telecommunications subsystem was a two-way radio system used for receiving and transmitting commands and data between the Mars Reconnaissance Orbiter and the Deep Space Network antenna on earth. With its large-dish antenna, powerful amplifier, and fast computer, Mars Reconnaissance Orbiter could transmit data to earth at rates as high as 6 megabits per second, a rate ten times higher than previous Mars orbiters. The orbiter's radio operated in the X-band of the radio spectrum, at a frequency of around 8 Gigahertz. Major components of the telecom subsystem included: * Antennas for transmitting and receiving commands * Amplifiers for boosting the power of radio signals so that they are strong enough to be received at the Deep Space Network antennas * Transponders for translating navigation and other signals from the orbiter Also on board was Electra, a UHF telecommunications package that was one of the engineering instruments providing navigation and communications support to landers and rovers on the surface of Mars. Electra allowed the spacecraft to act as a relay between the earth and landed crafts on Mars, which may not have sufficient radio power to communicate directly with earth. High-gain Antenna: The high-gain antenna is a 3-meter diameter (10-foot) dish antenna for sending and receiving data at high rates. The high-gain antenna was deployed shortly after launch and remained deployed for the remainder of the mission. It served as the primary means of communication to and from the orbiter. The high-gain antenna had to be pointed accurately and was therefore steered using the gimbal mechanism. Low-gain Antennas: Two smaller antennas were present for lower- rate communication during emergencies and special events, such as launch and Mars Orbit Insertion. The data rate of these antennas was lower because they focused the radio beam much more broadly than the high gain antenna, so less of the signal reached earth. But the Deep Space Network station on the earth could detect the signal even when the spacecraft was not pointed at earth, and therefore these antennas were useful for emergencies. The low-gain antennas had the capability to transmit and receive. The two low- gain antennas were mounted on the high-gain antenna dish--one on the front side and one on the back--and were moved with it. Two were needed in that placement so that communication was possible at all times, no matter what the position of the spacecraft might be at a given time. Amplifiers: Located on the backside of the high-gain antenna was the enclosure for the Traveling Wave Tube Amplifiers, which boosted the power of radio signals so that they were strong enough to be received at the Deep Space Network antennas. There were three amplifiers on board: * two for the X-band radio frequency that transmitted radio signals at a power of 100 watts (the second one was for back up to ensure communications in case the first amplifier failed) * one for Ka-band radio frequency that was capable of transmitting at 35 watts. Transponders: Mars Reconnaissance Orbiter carried two transponders, which are special types of radio receiver/transmitters, specially designed for long-range space communications. The second transponder was a backup. The transponders had several functions: * transmit/receive function: translated digital electrical signals into radio signals for sending data to earth, and translated radio signals to digital electrical signals for receiving commands from earth * transponding function: listened for and detected a signal coming in from earth, to which it automatically responded * navigation function: transmitted several types of signals that provided critical navigation clues, enabling navigators on the ground to make precise calculations of the spacecraft speed and distance from earth Propulsion: The propulsion subsystem performed major maneuvers such as trajectory correction maneuvers and Mars orbit insertion. The propulsion subsystem was also used to control the spacecraft's position, as a backup to the reaction wheels. Mars Reconnaissance Orbiter used a monopropellant propulsion system: it carried fuel (hydrazine), but no oxidizer. Thrust was produced by passing the fuel over beds of catalyst material just before it entered the thruster, which caused the hydrazine to combust. The propulsion system included: Propellant Tank The monopropellant hydrazine tank held 1187 kilograms (2617 pounds) of usable propellant. Over 70% of the total propellant was used during Mars orbit insertion. Pressurant Tank Mars Reconnaissance Orbiter fed pressurized helium gas from a separate high- pressure tank, through a regulator, into the propellant tank where it put the hydrazine propellant under pressure. Lines, Valves, and Regulators The pressurized hydrazine flowed through a system of metal tubing to each of the thrusters. Each thruster had a valve so that it could be fired independently. Additional valves in the propellant lines turned on and off the flow to groups of thrusters. Thrusters A total of 20 rocket engine thrusters were onboard: * Six large thrusters, each producing 170 Newtons* (38 pounds force) of thrust for performing the Mars orbit insertion burn. Together, all six produce 1,020 Newtons (230 pounds force) of thrust. * Six medium thrusters, each producing 22 Newtons* (5 pounds force) of thrust for performing trajectory correction maneuvers, and for helping to keep the spacecraft pointing in the right direction during the Mars orbit insertion burn. * Eight small thrusters, each producing 0.9 Newtons* (0.2 pounds force) of thrust for controlling where the orbiter is pointed during normal operations as well as during Mars orbit insertion and trajectory correction maneuvers. Command and Data-Handling Systems: The Command and Data Handling subsystem controlled all spacecraft functions. This system: * managed all forms of data on the spacecraft; * carried out commands sent from earth; * prepared data for transmission to the earth; * managed collection of solar power and charging of the batteries; * collected and processed information about all subsystems and payloads; * kept and distributed the spacecraft time; * calculated its position in orbit around Mars; * carried out commanded maneuvers; and * autonomously monitored and responded to any onboard problems that occurred. The key parts of this system were: * Space Flight Computer (a space-qualified processor based on the 133 MHz PowerPC processor) * Flight Software * Solid State Recorder (total capacity 160 Gigabits) Guidance, Navigation, and Control Systems: The guidance, navigation, and control subsystem was used to control the orientation of the orbiter as it travels through space and to maintain knowledge of where celestial bodies are located (for example, Earth and the sun). This knowledge was critical for the spacecraft to perform the correct maneuvers to get to Mars, to keep its solar arrays pointed toward the sun in order to produce power, and to keep its antenna pointed toward the earth in order to maintain communications. Once in orbit around Mars, this subsystem also maintained constant knowledge of where the spacecraft was in its orbit, and was able to point the science cameras to an accuracy of about 1/20th of one degree. Electrical Power: The electrical power subsystem was responsible for generating, storing, and distributing power to the orbiter systems and included two solar panels and two nickel-hydrogen batteries. Solar panels: The one and only source of power for Mars Reconnaissance Orbiter was sunlight. Mounted on opposite sides of the orbiter and capable of changing position to allow the orbiter to track the sun continuously, each solar panel had an area of approximately 10 square meters (107.6 square feet), and contained 3,744 individual solar cells. The solar cells were able to convert more than 26% of the sun's energy directly into electricity. The solar panels were deployed soon after launch and remained deployed throughout the mission. During aerobraking the solar panels had a special role to play. As the spacecraft skimmed through the upper layers of the martian atmosphere, the large, flat panels acted to slow the spacecraft down and reduce the size of its orbit. The solar arrays were designed to withstand temperatures of almost 200 Celsius. Nickel-hydrogen batteries: Mars Reconnaissance Orbiter used two nickel-hydrogen rechargeable batteries, each with an energy storage capacity of 50 ampere-hours (at 32 volts, 1600 watts per hour). Only about 40% of the battery capacity was intended to be used. The batteries charged during the day side of each two-hour orbit around Mars, using electricity produced by the solar cells, and provided power during the night side of each orbit. Thermal Systems: The thermal subsystem maintained the right temperatures in all parts of the spacecraft. It employed several conduction- and radiation-based techniques for thermal control: * Radiators * Surface coatings * Thermal blankets * Heaters. " END_OBJECT = INSTRUMENT_HOST_INFORMATION OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = "UNK" END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO END_OBJECT = INSTRUMENT_HOST END