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Find Out About the Different Structure, Power, Electronics and Telecommunication Systems Used in the Mars Reconnaissance Orbiter (MRO)
Now we continue with the fourth part of our blog on space science and technology. Those who have missed our third blog can read it from Here. It will help to connect with this fourth part of the blog discussing in details about the structure, power, electronic and telecommunication systems used in the Mars Reconnaissance Orbiter (MRO). Let us explore the blog to find out in more details. In words of Werner von Braun:
"A human being is the best computer available to place in a spacecraft. . . It is also the only one that can be mass produced with unskilled labor." "Our two greatest problems are gravity and paper work. We can lick gravity, but sometimes the paperwork is overwhelming." "I only hope that we shall not wait to adopt the program until after our astronomers have reported a new and unsuspected asteroid moving across their fields of vision with menacing speed. At that point it will be too late!"'
Structure of the Mars Reconnaissance Orbiter
Workers at Lockheed Martin Space Systems in Denver assembled the spacecraft structure and attached the instruments. Instruments were constructed at the Jet Propulsion Laboratory, the University of Arizona Lunar and Planetary Laboratory in Tucson, Arizona, Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, the Italian Space Agency in Rome, and Malin Space Science Systems in San Diego. The total cost of the spacecraft was $720 million USD. The structure is made of mostly carbon composites and aluminum-honeycombed plates. The titanium fuel tank takes up most of the volume and mass of the spacecraft and provides most of its structural integrity. The spacecraft's total mass is less than 2,180 kg (4,810 lb) with an unfuelled dry mass less than 1,031 kg (2,273 lb).
Power Systems
MRO gets all of its electrical power from two solar panels, each of which can move independently around two axes (up-down, or left-right rotation). Each solar panel measures 5.35 m × 2.53 m (17.6 ft × 8.3 ft) and has 9.5 m2 (102 sq ft) covered with 3,744 individual photovoltaic cells. Its high-efficiency triple junction solar cells are able to convert more than 26% of the Sun's energy directly into electricity and are connected together to produce a total output of 32 volts. At Mars, each of the panels produces more than 1,000 watts of power; in contrast, the panels would generate 3,000 watts in a comparable Earth orbit by being closer to the Sun. MRO has two rechargeable nickel-hydrogen batteries used to power the spacecraft when it is not facing the Sun. Each battery has an energy storage capacity of 50 ampere-hours (180 kC). The full range of the batteries cannot be used due to voltage constraints on the spacecraft, but allows the operators to extend the battery life—a valuable capability, given that battery drain is one of the most common causes of long-term satellite failure. Planners anticipate that only 40% of the batteries' capacities will be required during the lifetime of the spacecraft.
Electronic Systems
MRO's main computer is a 133 MHz, 10.4 million transistor, 32-bit, RAD750 processor. This processor is a radiation-hardened version of a PowerPC 750 or G3 processor with a specially built motherboard. The RAD750 is a successor to the RAD6000. This processor may seem underpowered in comparison to a modern PC processor, but it is extremely reliable, resilient, and can function in solar flare-ravaged deep space. The operating system software is VxWorks and has extensive fault protection protocols and monitoring. Data is stored in a 160 Gb (20 GB) flash memory module consisting of over 700 memory chips, each with a 256 Mbit capacity. This memory capacity is not actually that large considering the amount of data to be acquired; for example, a single image from the HiRISE camera can be as large as 28 Gb.
Telecommunications Systems
The Telecom Subsystem on MRO is the best digital communication system sent into deep space so far and for the first time using capacity approaching turbo-codes. The Electra communications package is a UHF software-defined radio (SDR) that provides a flexible platform for evolving relay capabilities. It is designed to communicate with other spacecraft as they approach, land, and operate on Mars. The system consists of a very large (3 m (9.8 ft)) antenna, which is used to transmit data through the Deep Space Network via X-band frequencies at 8 GHz, and it demonstrates the use of the Ka band at 32 GHz for higher data rates. Maximum transmission speed from Mars is projected to be as high as 6 Mbit/s, a rate ten times higher than previous Mars orbiters. The spacecraft carries two 100-watt X-band amplifiers (one of which is a backup), one 35-watt Ka-band amplifier, and two Small Deep Space Transponders (SDSTs). Two smaller low-gain antennas are also present for lower-rate communication during emergencies and special events, such as launch and Mars Orbit Insertion. These antennas do not have focusing dishes and can transmit and receive from any direction. They are an important backup system to ensure that MRO can always be reached, even if its main antenna is pointed away from the Earth.
Altitude Control
he spacecraft uses a 1,175 L (258 imp gal; 310 US gal) fuel tank filled with 1,187 kg (2,617 lb) of hydrazine monopropellant. Fuel pressure is regulated by adding pressurized helium gas from an external tank. Seventy percent of the propellant was used for orbital insertion, and it has enough propellant to keep functioning into the 2030s. MRO has twenty rocket engine thrusters on board. Six large thrusters each produce 170 N (38 lbf) of thrust for a total of 1,020 N (230 lbf) meant mainly for orbital insertion. These thrusters were originally designed for the Mars Surveyor 2001 Lander. Six medium thrusters each produce 22 N (4.9 lbf) of thrust for trajectory correction manoeuvres and attitude control during orbit insertion. Finally, eight small thrusters each produce 0.9 N (0.20 lbf) of thrust for attitude control during normal operations. Four reaction wheels are also used for precise attitude control during activities requiring a highly stable platform, such as high-resolution imaging, in which even small motions can cause blurring of the image. Each wheel is used for one axis of motion. The fourth (skewed) wheel is a backup in case one of the other three wheels fails. Each wheel weighs 10 kg (22 lb) and can be spun as fast as 100 Hz or 6,000 rpm. A primary and backup Miniature Inertial Measurement Unit (MIMU), provided by Honeywell, measures changes to the spacecraft attitude as well as any non-gravitational induced changes to its linear velocity. Each MIMU is a combination of three accelerometers and three ring-laser gyroscopes. These systems are all critically important to MRO, as it must be able to point its camera to a very high precision in order to take the high-quality pictures that the mission requires. It has also been specifically designed to minimize any vibrations on the spacecraft, so as to allow its instruments to take images without any distortions caused by vibrations.
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