Lunar Crater Observation and Sensing Satellite

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Lunar Crater Observation and Sensing Satellite

LCROSS SS / C and EDUS before cutting
NSSDC ID 2009-031B
Mission goal Earth moon
Client NASA
Launcher Atlas V
construction
Takeoff mass 891 kg
Instruments

9

Course of the mission
Start date June 18, 2009
launch pad Cape Canaveral AFS Launch Complex 41
End date October 9, 2009
 
06/18/2009 begin
 
06/23/2009 Fly by the moon, entry into a very high, polar earth orbit
 
October 9, 2009 Separation of SS / C and EDUS
 
October 9, 2009 Impact on the moon
LCROSS SS / C in the foreground, with a detached EDUS stage that is accelerating towards the moon

LCROSS ( LCROSS ) was the name of a spacecraft of NASA , which on 18 June 2009 at 21:32 UTC along with the Lunar Reconnaissance Orbiter (LRO) to the Moon launched on 9 October 2009 at the moon struck. It was hoped that the LCROSS mission would create an artificial crater to obtain definitive knowledge about the existence of water ice at the south pole of the moon, which could play an important role for future manned lunar missions .

planning

LCROSS was an additional payload of LRO probe came after NASA decided in December 2005, LRO with a Delta IV or Atlas V - launcher instead of the much weaker Delta II launch. The Delta II only has a spin-stabilized upper stage, which did not meet the requirements for the start of the LRO. The use of the stronger atlas made it possible to take an additional payload, such as an impactor, lander or a separate communication microsatellite, to the moon. After NASA had received several proposals for an additional payload as part of a tender , the LCROSS mission was announced on April 10, 2006 as the final winner of this tender. On July 28, 2006, NASA announced that the launch would be with an Atlas-V (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 only separated when approaching the south pole of the moon. EDUS, which was nothing more than the Centaur upper stage of the launcher, was to hit near the South Pole a short time later and create a cloud of particles, with about 1000 tons of lunar material being ejected. Then the Shepherding spacecraft flew through the cloud, analyzed it with the help of its instruments, before it also hit the moon. The whole event should be observed in parallel from the LRO as well as from satellites and telescopes in orbit and from the earth's surface.

Mission history

Start and shot on lunar orbit

LCROSS took off together with LRO on June 18 at 21:32 UTC on an Atlas V rocket. This brought the probes into a parking orbit around the earth. After 24 minutes, the engines of the Centaur upper stage were fired again, setting the combination on course into a polar lunar orbit. Shortly afterwards the missile was rotated 180 ° and LRO released. By pulsing the engines, the trajectory of the rest of the rocket was changed so that LCROSS and the Centaur flew past the southern lunar pole and entered a polar lunar orbit. After the maneuver, the engines were used to consume as much fuel as possible so that LCROSS 'measurement results of the upstroke were not falsified by residual fuel from the Centaur. About four hours after take-off, the empty Centaur was declared a LCROSS payload.

Flight history

In the next few days after take-off, three course corrections were made and on June 23, LCROSS flew by with the Centaur level still connected to the moon. The minimum distance was 3200 km. The area of ​​the Mendeleev crater was examined from a distance of about 8,000 km . The further flight path led over the craters Goddard C and Giordano Bruno . Due to the swing-by effect, the probe entered a very high orbit that extends far beyond the lunar orbit. The new orbit of LCROSS was tuned so that the probe completes two orbits while the moon orbits the earth three times, so that the probe did not come close to the moon until October 9th. During these two cycles, the systems were checked and calibrated. Several course corrections were planned, the last two 72 and 11 hours before the impact.

On August 22nd it was found that the probe had used up 140 kg of its fuel (75%) to correct its position with the control nozzles due to a temporary error in the inertial sensor (IRU Inertial Reference Unit). According to estimates by the operating team, the remaining amount of fuel with a reserve of 9 to 18 kg was just sufficient for a successful mission completion.

A hit

Centaur's target area, recorded by the Shepherding Spacecraft from an altitude of 700 km shortly before the impact

The target of the impact on October 9 was in the western part of the 95 km Cabeus crater , a permanent shadow area near the South Pole. The original plan was to plunge the probe into an unnamed crater 17 km in diameter on the edge of the 48 km large Cabeus A. Based on more recent satellite data, it was hoped that the new target would result in a higher hydrogen concentration and better lighting conditions. Almost ten hours before the impact, LCROSS split into the Centaur upper level and the Shepherding Spacecraft. While the Centaur continued to fly and crashed at 11:31 UTC at a speed of 2.5 km / s at an angle of about 70 ° on the moon, LCROSS reduced its speed and thereby gained a total of about four minutes distance from the upper level by the time it hit. In these four minutes, the ejection cloud of the Centaur impact was supposed to develop, so that LCROSS could collect scientific data on its composition as it passed through and transmit it to earth in real time before it hit at 11:36. After the ejection cloud was initially not visible during the live broadcast from the moon, the impact could be identified a little later on infrared images taken from a distance of 600 km. With instruments of the LRO , which flew over the crash site at a distance of 77 km, the ejection cloud could be recorded with the UV spectrometer (LAMP) and the impact crater with the imaging radiometer (DLRE).

The LRO, several earth-based telescopes and also the Hubble space telescope tracked the event. In preparation for this, numerous maps and photos were published to identify the target area. The impact should already be observed with larger amateur telescopes, but it turned out that even the observatories Keck and Gemini in Hawaii showed no signs of the impact in the visible area. Apparently the cloud of debris was smaller than hoped, which the public received with disappointment. The basis for the scientific evaluation are the optical spectra that were recorded by various sensors and whose evaluation will take some time. The amount of hydroxyl in the resulting cloud allows conclusions to be drawn about the content of water or ice in the crater.

Technical specifications

  • Weight: 891 kg (585 kg probe + 306 kg hydrazine as fuel)
  • Dimensions: 2 m × Ø 2.6 m (3.3 m with antennas), 12.7 m × Ø 3.0 m (Centaur)
  • Energy 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 transponder with a maximum transmission rate of 1.5 Mbit / s
  • Payload: two spectrometers working in the near infrared range, one spectrometer working in the UV to visible range, two cameras working in the medium infrared range, two cameras working in the near infrared range and one camera system and high-speed photometer each working in the visible range

Quantity of the occurrence of water

On November 13, 2009, NASA reported several signs that confirm the existence of water in the cloud created by the Centaur's impact on the moon. The concentration and distribution of the water and the other substances require further analysis. Further confirmation comes from the ultraviolet spectrometric analysis, which confirms the existence of hydroxyl , a product that arises from the splitting of water under the influence of the sun's rays. The amount of water found was described by Robert Zubrin as follows: “Approx. 10 million kg of regolith emerged from the 30-meter crater . About 100 kg of water were found in it. This corresponds to 10  ppm ; that is a proportion that is smaller than that of the driest desert on earth. In comparison: We found large regions on Mars with a water content of 600,000 ppm, which means 60% water. "

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

See also

Web links

Commons : Lunar Crater Observation and Sensing Satellite  - collection of images, videos and audio files

swell

  1. ^ Nasa Missions Homepage , June 15, 2009
  2. ^ NASA: New NASA Ames Spacecraft to Look for Ice at Lunar South Pole , April 10, 2006
  3. NASA: NASA Awards Launch Services for Lunar Mission July 28, 2006
  4. ^ Spacecraft Anomaly. NASA, August 25, 2009; archived from the original on July 17, 2012 ; accessed on September 14, 2009 .
  5. ^ Fuel Drain Hinders LCROSS. Aviation Week, August 27, 2009 (English)
  6. NASA's LCROSS Mission Changes Impact Crater. NASA, September 28, 2009, accessed September 29, 2009 .
  7. NASA'S LCROSS Reveals Target Crater for Lunar South Pole Impacts. NASA, September 11, 2009, accessed September 13, 2009 .
  8. Here - in the IR - the fresh Centaur crater lights up! October 9, 2009, accessed October 10, 2009 .
  9. Lunar Reconnaissance Orbiter Update: LRO Observes LCROSS Impact! October 9, 2009, accessed October 10, 2009 .
  10. LCROSS and impactor: impact in a moon crater . raumfahrer.net, October 9, 2009.
  11. NMSU / MSFC LCROSS Ground based Impact Observations (English)
  12. Stephen Clark: Lunar smash produces surprise, disappointment. Spaceflight Now, October 9, 2009, accessed October 10, 2009 .
  13. NASA: LRO / LCROSS Press Kit (PDF; 2.6 MB)
  14. ^ Zubrin: Congratulations NASA, You've Discovered Greenland
  15. Michael Braukus: LCROSS Results Released. NASA, October 21, 2010, accessed April 12, 2020 .