LCROSS

Lunar Crater Observation and Sensing Satellite ( LCROSS ) was the name of a spacecraft of NASA, at 21:32 UTC, together with the Lunar Reconnaissance Orbiter ( LRO ) is launched to the Moon on 18 June 2009 and 9 October 2009 on the moon struck. From the LCROSS mission was hoped by creating an artificial crater definitive findings about the presence of water ice at the lunar south pole to obtain, which could play an important role for future manned lunar missions.

Planning

LCROSS was an additional payload of the LRO probe, which came after NASA decided in December 2005 to launch LRO with a Delta IV or Atlas V launch vehicle instead of the much weaker Delta II. The Delta II has only a spin- stabilized upper stage, which did not meet the requirements for the launch of LRO. The use of the more powerful Atlas showed the possibility of an additional payload, such as an impactor, Lander or a separate communication microsatellites to take to the moon. After NASA had received several proposals of an additional payload in a tender, the LCROSS mission was announced as the final winner of this tender on 10 April 2006. On 28 July 2006, NASA announced that the launch of an Atlas V will be (401 ) launcher.

Construction

LCROSS consisted of two separate parts: the Shepherding Spacecraft (SS / C) and the Earth Departure Upper Stage ( EDUS ), which remained connected on the way to the moon and were separated only when approaching the south pole of the moon. EDUS, which was nothing more than the Centaur upper stage of the launcher should open a short time later near the south pole, creating a cloud of particles, with about 1,000 tons of lunar material should be ejected. Subsequently, the Shepherding Spacecraft flew through the cloud, they analyzed with the help of his instruments before it also hit the moon. The whole event should be observed in parallel by the LRO as well as satellites and telescopes in Earth orbit and from the surface.

Mission History

Start and bullet to lunar orbit

LCROSS launched with LRO on June 18 at 21:32 UTC on an Atlas V rocket. This brought the probes in a parking orbit around the Earth. After 24 minutes, there was a further ignition of the engines of the Centaur upper stage, which brought the combination on track in a polar lunar orbit. Shortly after the rocket has been rotated through 180 ° and dissolved LRO. By pulsing of the engines changed to the path of the rest of the rocket so that LCROSS and the Centaur fly past at the lunar South Pole and entered into a polar lunar orbit. After the maneuver, the engines were used to consume as much fuel as possible, so LCROSS ' measurement results of the surcharge are not distorted by fuel residues of the Centaur. About four hours after the start of the empty Centaur was declared a payload of LCROSS.

History of the flight

In the next few days after the start made ​​three course corrections and on 23 June the flyby of LCROSS Centaur associated with the still - stage at the moon. The minimum distance was 3200 km. From about 8000 km from the area of the crater Mendeleev was investigated. The additional flight path led along the caldera Goddard C and Giordano Bruno. By the swing-by effect, the probe entered a very high Earth orbit that extends far beyond the Moon's orbit. The new orbit of LCROSS was tuned so that the probe takes two rounds, while the moon orbits the Earth three times, so that the probe came again until October 9, close to the Moon. During these rounds of both the systems were tested and calibrated. There were several course corrections provided the last two 72 and 11 hours before the impact.

On August 22, it was found that the probe due to a transient fault in the inertial sensor (IRU Inertial Reference Unit) had used up unscheduled 140 kg of their fuel (75%) to position correction with the steering jets. According to estimates by the operating crew, the amount of fuel remaining with a reserve of 9 to 18 kg for a successful mission completion was just adequate.

Impact

The aim of the strike on October 9, was in the western part of the 95 - km crater Cabeus, a permanent shadow area near the South Pole. It was originally planned to leave the probe in an unnamed crater 17 km in diameter fall at the edge of the 48 km wide Cabeus A. Based on more recent satellite data it was hoped that the new target a higher hydrogen concentration and better light conditions. Almost ten hours before the LCROSS impact is separated into the Centaur upper and the Shepherding Spacecraft. While the Centaur flew on and at 11:31 UTC s at an angle of about 70 ° crashed at a speed of 2.5 km / to the moon, LCROSS reduced its speed and thereby gained to impact a total of about four minutes distance to college. In these four minutes, the ejection cloud of Centaur strike should develop so that LCROSS was able to collect while traversing scientific data on their composition and spark in real time to the ground before he even opened at 11:36. After the ejection cloud was not initially in the live broadcast from the moon visible, the impact could a little later on infrared images, taken from 600 km away, can be identified. With the LRO instruments, flew over the crash site in 77 km distance, could ( DLRE ) of impact craters are recorded with the UV spectrometer ( LAMP), the ejection cloud and with the imaging radiometer.

The LRO, several ground-based telescopes and the Hubble Space Telescope followed the event. In preparation for this, numerous maps and photographs for identification of the target area have been published. The impact should already be observed with larger amateur telescopes, but it turned out that even the Keck and Gemini observatories in Hawaii in the visible region showed no signs of impact. Apparently, the debris cloud was less than hoped for, what was included in public with disappointment. Basis for the scientific evaluation of the optical spectra, which were recorded by various sensors and their evaluation will take some time to complete. The amount of hydroxyl in the resulting cloud allows conclusions on the content of water or ice in the crater.

Specifications

• Mass: 891 kg ( 585 kg 306 kg probe hydrazine as fuel)
• Dimensions: 2 m × Ø 2.6 m ( 3.3 m with antennas), 12.7 m × Ø 3.0 m ( Centaur )
• Power supply: solar cells with 600 watts of power and lithium - ion batteries
• Stabilization: star sensor and ten sun sensors
• Telemetry: transmission by a 7 -watt S -band transponders with up to 1.5 MBit / s transfer rate
• Payload: two operating in the near infrared spectrometer, one in the UV to visible range working spectrometer, two operating in the mid-infrared cameras, two operating in the near infrared cameras and one working in the visible range camera system and high-speed photometer

Quantitative indication on the occurrence of water

On 13 November 2009, NASA reported on several signs that confirm the existence of water in the cloud caused by the impact of the Centaur on the moon. However, the concentration and distribution of the water and other substances need further analyzes. A further confirmation of results from the spectrometric analysis in the ultraviolet range, which confirms the existence of hydroxyl, a product resulting from the splitting of water under the influence of sun rays. The amount of water found was described by Robert Zubrin as follows: " From the resulting 30-meter crater about 10 million kilograms of regolith have emerged. This approximately 100 kg of water were found. This corresponds to 10 ppm; which is a percentage that is less than that of the driest desert on earth. In comparison: We have a water content of 600,000 ppm found on Mars large regions, 60% water "means.

On 21 October 2010, NASA published further data, which are still considerable amounts of water and other volatile substances could be detected in the dust cloud.