 Minisat 01 mission patch | |
| Operator | INTA |
|---|---|
| COSPAR ID | 1997-018A |
| SATCATno. | 24779 |
| Mission duration | 5 years |
| Spacecraft properties | |
| Launch mass | 195 kg |
| Start of mission | |
| Rocket | Pegasus-XL |
| Payload | |
| EURD, CPLM, LEGRI, ETRV | |
TheMinisat 01 was a satellite developed in Spain as a means to kickstart its space program. The project started in 1990 and was funded by both the Inter-Ministerial Committee of Space Science and Technology (CICYT) and theInstituto Nacional de Técnica Aeroespacial (INTA) who was also responsible for the project's management. After some feasibility studies, the satellite entered the design phase in 1993. The main objectives of the program were to develop atechnology demonstrator to test and develop the nation's capabilities to produce and manage spacecraft. To this end, INTA teamed up with private enterprises and universities to acquire funds and resources. Nonetheless, emphasis was also put on keeping the costs to a minimum and to ensure affordability.[1]
The initial program was supposed to involve at least four minisatellites (Minisat 1 to 4) but only Minisat 01 was put into orbit. A second design, the Minisat 02, was developed and tested in 2001 but the mission was canceled and the satellite was scrapped by 2002.[2]
The Minisat 01 was conceived to performEarth observation on alow orbit in addition to four different scientific experiments:[3]
An alternative payload was devised but not implemented consisting on four additional experiments: GOYA (Gamma-ray burst Observer Yearned-Always), SIXE (Spanish Italian X-ray Experiment), DOPA, XRASE. These experiments would be later projected for the Minisat 02 before the whole project was scrapped.[4]
The satellite was built betweenCASA, who was in charge of developing the platform, and INTA, who mainly devised the different payload and experiment implementation. A great degree of emphasis was put on keeping cost down so the construction wasmodular (able to allocate up to 300 kg of payload), small (about 1145 mm x 1005 mm x 1170 mm) and projected to have a service life of 4 to 5 years. The body ended up weighing 195 kg (100 kg structure and 95 kg of payload) and was shaped like ahexagonal prism with the experiments attacked to the top and bottom faces while the sides mounted 4 deployableAsGasolar panels (550 mm x 800 mm in size) capable each to fully provide the power needed to run the satellite (about 50 W).[5]
The core contained aNiCd battery and the onboard central computing and processing unit (a modifiedIntel 80386 microprocessor) with 32Mb ofRAM, 512 kb ofEEPROM, 2.4MIPS of throughput, 32 MB ofdata storage and multipleredundant cores. A bus connection links the microprocessor to the experiments capable of providingpoint-to-point interfaces while managing the control subsystem. This was divided in two basic units: the thermal and the kinetic units. The first consisted of insulator coating around the body with both, internal and external,thermistors to measure temperature and active internal heaters around experiments and battery to keep the temperature within operational ranges. The kinetic unit ensured the Minisat 01 maintained a favorable position to maximizesunlight incidence on the solar panels in addition to stabilize the spacecraft on its 3 axis. This unit consisted on a combination of 3torque rods placedorthogonally to each other and areaction wheel in the spin plane. Data of the current position of the body was provided by two perpendicularly putSun sensors and two biaxialmagnetometers which, working in cooperation, could provide accurate information on the satellite's position up to ±3º oferror.[6]
Communication with Earth was maintained using bidirectionalRF transmitters operating on theS-band with adownlink speed of 1 Mbit/s and an uplink speed of 2 kbit/s.
The S/C was launched from an AmericanLockheed L-1011-385-1-15 TriStar registered N140SC[7] with aPegasus-XL rocket fromGando Air Base in theCanary Islands 21 April 1997.[8] It was successfully put on a near-circular closeorbit of 585 km ofapoapsis and 566 km of periapsis with and inclination of 151º (29ºretrograde) and an orbitalperiod of 96 minutes.[9]
The mission included the launch of the cremated remains ofGene Roddenberry,[10]Timothy Leary,Gerard K. O'Neill along with those of 21 other people.[11][12]
After 5 years of successful operation, the satellite reentered the atmosphere on 14 February 2002.
During its whole service life it was operated by INTA, who monitored the satellite from theMaspalomas Station (15º 37' 45" W, 27º 45' 49" N).[13]
Being the result of the joint efforts of INTA and theUniversity of California, Berkeley, this device was to conductspectrographic observations of diffuseEUV radiation in the interstellar medium to examine theMesosphere's composition. The focus of these observations were oxygen lines and high energy (above 10eV), high mean life (above 1024 s)neutrinos whose presence may be indicative ofdark matter.
To achieve that, the device employed two independentspectrometers equipped with modulablespectral band (between 350 and 1100 Å). This allowed to compare andfilter the readings obtained to minimizesystematic errors caused by theionizing nature of EUV, thus, ensuring a higher degree of precision. Each spectrometer was about 40x40x13 cm in size and 11 kg in weight with acutegrating (8 cm of diameter, 18 cm offocal length with holographically ruled 2460 lines/mm and made ofsilicon/boroncarbide) to protect the measuring instruments. Under the grating, the Multi-Channel Plate (MCP) detectors with wedge and strip encoding are allocated, facing the exterior through alens which provides them with 26º x 8ºFOV and four possible positions. These were: open (transmitting all wavelength), shielded (blocks all emission and allows for internal radiation readings),magnesium fluoride filter (which allows to measureLyman-alpha spectral series), and aluminum filter (which blocks most of the Lyman radiation while letting EUV through).
The device was placed at one end of the satellite, facing an anti-sun direction and it was operated continuously during the satellite's life.[14]
Developed by theTechnical University of Madrid the CPLM was experimentation module created to study thebehavior of fluids when allocated inside axis-symmetric bridges under conditions ofmicrogravity. It consisted of a test cell containing the fluid bridges embedded between severaloptical detectors, which were capable of measuring changes in position and shape of the fluid, and a command unit. This unit was itself built with amotor, able to change the direction of the bridges and to reset the experiment, and anaccelerometer which measured the forces acting on the test fluid. The module was allocated inside a cylindrical container which also held thepower supply, severaltemperature andpressure sensors, and a back-upmemory card.
During its operational run, the liquid bridge would be oriented perpendicular to the z-axis (Sun-to-satellite direction) and activated for 5 minutes once a week. As a result, the satellite wouldspin ±0.375rpm longitudinally as a direct consequence from the accelerations applied at the CPLM.[15]
The LEGRI was developed by an international composed by INTA, theRutherford Appleton Laboratory (RAL), theUniversity of Valencia, and theUniversity of Birmingham. The main objective was to build aprototypegamma-ray telescope capable of detecting low energy radiation (between 10 and 200 keV) produced by thedispersion ofgamma radiation emitted by celestial bodies such asblack holes,binary stars orneutron stars.
The device was to incorporate some cutting-edge technology for its time, such asHgI2 emerging detectors developed by theCentro de Investigaciones Energéticas y Medioambientales (CIEMAT) capable of providing accurate readings on the operating energy range and a high degree ofthermal resistance and a very good efficiency-weight ratio. Originally, 100 such detectors were to form the LEGRI sensing sub-unit but the experimental nature of this technology made INTA choose to mix an array of 80 HgI2 20, more conventional and reliableCdZnTe detectors. This decision also allowed them to directly compare their performance when working on a0 g environment and sharingFEE andbackground noise fluxes. Besides the sensing sub-unit, LEGRI incorporated a filtering unit made of a mechanicalcollimator supported on ahoneycombtungsten plate which is allocated in front of the detectors, a high voltage power supply needed to feed the device, and a processing unit which manages data and provides continuousattitude readings on the satellite to easeimage reconstruction while avoidingsignal noise.[16]
Developed by CASA, the ETRV was aspeed regulation mechanism capable of deploying various devices such as solar panels, antennas, and proves. It consisted of an electrical motor connected atorsion spring mounted over agearbox capable of regulating motion and providing a certain degree of stability. To simulatepayloads, a smallflywheel was added to the end of a deploying arm directly connected to the gearbox. To ensure the correct positioning of the movable arm an electromagneticReed switch would measuremomentum, gyro angle, and rate of the arm providing real-time corrections for the system and allowing a maximum deployment speed of 180º in about 3 minutes.
The time control during the different phases of deployment was ensured by apyrotechnic nut, responsible for maintaining the system's integrity until the firing of a pyro-kintetic charge which would signal the conditions were met to begin the whole placement process.[17]
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