| Piú viste - The Clementine Files |
000-Clementine.gif000 - Clementine82 visiteDescription
Clementine was a joint project between the Ballistic Missile Defense Organization (BMDO, nee the Strategic Defense Initiative Organization, or SDIO) and NASA. The objective of the mission was to test sensors and spacecraft components under extended exposure to the space environment and to make scientific observations of the Moon and the near-Earth asteroid 1620 Geographos. The Geographos observations were not made due to a malfunction in the spacecraft. The lunar observations made included imaging at various wavelengths in the visible as well as in ultraviolet and infrared, laser ranging altimetry, gravimetry, and charged particle measurements. These observations were for the purposes of obtaining multi-spectral imaging the entire lunar surface, assessing the surface mineralogy of the Moon and obtaining altimetry from 60N to 60S latitude and gravity data for the near side. There were also plans to image and determine the size, shape, rotational characteristics, surface properties, and cratering statistics of Geographos. Clementine carried 7 distinct experiments on-board: a UV/Visible Camera, a Near Infrared Camera, a Long Wavelength Infrared Camera, a High Resolution Camera, two Star Tracker Cameras, a Laser Altimeter, and a Charged Particle Telescope. The S-band transmitter was used for communications, tracking, and the gravimetry experiment.
Spacecraft and Subsystems
The spacecraft was an octagonal prism 1.88 meters high and 1.14 m across with two solar panels protruding on opposite sides parallel to the axis of the prism. A high-gain fixed dish antenna was at one end of the prism, and the 489 N thruster at the other end. The sensor openings were all located together on one of the eight panels, 90 degrees from the solar panels, and protected in flight by a single sensor cover. The spacecraft propulsion system consisted of a nonpropellant hydrazine system for attitude control and a bipropellant nitrogen tetraoxide and monomethyl hydrazine system for the maneuvers in space. The bipropellant system had a total capability of about 1900 m/s with about 550 m/s required for lunar insertion and 540 m/s for lunar departure. Attitude control was achieved with 12 small attitude control jets, two star tracker cameras, and two inertial measurement units. The spacecraft was three-axis stabilized in lunar orbit via reaction wheels with a precision of 0.05 Deg. in control and 0.03 Deg. in knowledge. Power was provided by gimbaled, single axis, GaAs/Ge solar panels which charged a 15 amp-hour, 47-w hr/Kg Nihau (Ni-H) common pressure vessel battery. Spacecraft data processing was performed using a MIL-STD-1750A computer (1.7 million instructions per second) for savemode, attitude control, and housekeeping operations, a RISC 32-bit processor (18 million ips) for image processing and autonomous operations, and an image compression system provided by the French Space Agency CNES. A data handling unit sequenced the cameras, operated the image compression system, and directed the data flow. Data was stored in a 2 Gbit dynamic solid state data recorder.
Mission Profile
The mission had two phases. After two Earth flybys, lunar insertion was achieved approximately one month after launch. Lunar mapping took place over approximately two months, in two parts. The first part consisted of a five hour elliptical polar orbit with a periapsis of about 400 Km at 30 degrees south latitude and an apoapsis of 8300 Km. Each orbit consisted of an 80 minute lunar mapping phase near periapsis and 139 minutes of downlink at apoapsis. After one month of mapping the orbit was rotated to a periapsis at 30 degrees north latitude, where it remained for one more month. This allowed global imaging and altimetry coverage from 60 degrees south to 60 degrees north, over a total of 300 orbits. After a lunar/Earth transfer and two more Earth flybys, the spacecraft was to head for Geographos, arriving three months later for a flyby, with a nominal approach closer than 100 Km. Unfortunately, on May 7, 1994, after the first Earth transfer orbit, a malfunction aboard the craft caused one of the attitude control thrusters to fire for 11 minutes, using up its fuel supply and causing Clementine to spin at 80 rpm. Under these conditions, the asteroid flyby could not yield useful results, so the spacecraft was put into a geocentric orbit passing through the Van Allen radiation belts to test the various components on board. The mission ended in June 1994 when the power level onboard dropped to a point where the telemetry from the spacecraft was no longer intelligible.
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051-The Moon from Clem-Aristarchus.jpg043 - Aristarchus Plateau (natural colors)82 visiteA mosaic of more than 250 images showing the complex and diverse Aristarchus Region of the Moon in approximately natural colors (blue = 415 nanometers, green = 750 nanometers, red = 950 nanometers). The plateau is an uplifted block of complex, highland terrain, partly flooded by later mare basalt lavas. Dark, pyroclastic glasses partly cover the uplifted terrain. The crater Aristarchus (47 Km in diameter) has formed in the South-East corner of the plateau, excavating both highlands and mare rocks.
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082-The Moon from Clem-NorthPole.jpg113 - Polar Areas: Views of the North Pole82 visiteMosaic of about 750 Clementine images of the North Pole of the Moon, from 80° North Lat. to the Pole (center). The Near-Side of the Moon is the bottom half of this mosaic and the top half is on the Far-Side. In contrast to the South Pole (slide #111), the North Pole shows very little area in permanent shadow (only about 500 square-Km). This suggests that any "cold traps" in this Region of the Moon are very restricted and little ice could be stable in this part of the Moon.
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ZZ-Farside-Clem.jpg008 - Far-Side Map82 visitenessun commento
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022-The Moon from Clem-FroelichCrater.gif081 - Froelich Crater81 visitenessun commento
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Moon_Full-STB.jpg026 - Earthshine81 visitenessun commento
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035-The Moon from Clem-PolarAreas.jpg111 - Polar Areas: Views of the South Pole80 visiteThe spin axis of the Moon is nearly vertical (inclined 1,6°) to the ecliptic plane (the plane of its orbit around the Sun), in marked contrast to the Earth (axis inclination 23,5°). However, even this small inclination means that the hemispheres of the Moon experience seasons as the Pole tracks toward and away from the Sun. Clementine started its lunar mapping in the dead of Southern Winter (axis away from the Sun), but by the 2nd month of mapping, the axis had begun to point closer in that direction. These two mosaics show the difference in lighting conditions between the first month of mapping (left, maximum winter) and the second month's coverage (right, toward the solstice).
Careful examination of the two mosaics reveals some slight shadow changes; note in particular the shadows that cover the floors of the craters Amundsen and Scott (large central peak crater at about 3 o'clock and the crater just above it). However, the large region of permanent shadow near the center of the mosaics discovered by Clementine remains virtually unchanged in the two mosaics.
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090-The Moon from Clem-KeplerCrater.jpg152 - Kepler Crater80 visitenessun commento
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LUB20121.gif183 - Rydberg Crater and surroundings80 visitenessun commento
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ZZ-IceontheMoon.jpg115 - Where is the "Lunar Ice"?80 visitenessun commento
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002-The Moon and Planets from Clem.JPG020 - The Moon and a few planets79 visiteThe Startracker imaged this spectacular shot of the sunrise, planets, and Moon. This color-enhanced image shows, from right to left, the Moon lit by the Earth, the terminator - or boundary between light and dark - into the dark side with the solar corona just rising over the limb, and the bright planets Saturn, Mars, and Mercury. Several dimmer stars can also be seen. The Startracker algorithm achieved a star match, realizing that the Sun and planets were not in the correct position to be stars, and ignored them.
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OrientaleBasin&SC~0.JPG027 - Earthshine and Solar Corona over the Orientale Basin79 visiteThis fantastic view of the Moon was acquired by the Attitude Determination Camera (Startracker) on board Clementine.
The Moon is illuminated only by Earthshine - that is, sunlight reflected from the Earth to the Moon.
The Sun is actually behind the Moon, though the outer portion of the Sun, the Solar Corona, is visible over the limb.
The ringed basin disappearing into the darkness is the Orientale Basin.
deep shadows cast by its steep walls give a dramatic emphasis to its classic multi-ring morphology.
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