The Lunar Reconnaissance Orbiter (LRO) is the first probe of NASA's "Robotic Lunar Exploration Program", which was launched on June 18, 2009 with the God-5 carrier rocket.The mission objective is to draw the lunar characteristics and lunar resource network for the design and construction of future lunar outposts.In addition, the probe also conducts the selection of safe landing sites, identification of lunar resources, research on the impact of lunar radiation on humans, and verification of new technologiesNASAThe Goddard Space Flight Center (GSFC) was developed, and the whole project cost about 491 million dollars, of which the launch cost was 136 million dollars.
In the 21st century, a new upsurge of lunar exploration has sprung up again in the world's major space faring countries. The goal is to explore the lunar resources, test the exploration technology, and prepare for the development of lunar energy and resources.In January 2004, President Bush of the United States announced the "new concept of space exploration".On September 19, 2005,NASA(NASA) Director Michael Griffin announced a 104 billion dollar budget plan to return to the moon in Washington, D.C., which is expected to use a new manned spacecraft to send humans to the moon again before 2020.LRO mission is a part of the above plan, which focuses on applied science/engineering assessment. The main objectives include: selecting landing sites for future robot and human exploration of the moon;Identify potential lunar resources.[1]
Detector overview
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The United States plans to return to the moon within ten years, launch a robotic lunar lander to the moon, and then land a man on the moon again.In preparation for this grand plan, NASA launched the Lunar Reconnaissance Orbiter (LRO) probe in 2009.
The purpose of LRO mission is to survey possible landing points;Assess the water and other resources on the moon, including the sunlight that can be used to generate electricity;Describe the radiation environment astronauts may face in the future.[2]
After entering the final lunar exploration orbit, LRO will carry out a one-year exploration mission in polar orbit 30 to 50 meters high.After that, it may enter the low maintenance orbit to carry out the extended mission for up to five years, continue the survey work or use it as a lunar communication relay satellite.
LRO is a three-axis stable platform with the ability to store and send data in real time.It is estimated that the data transmission speed of LRO is about 100 megabits per second, and the observation data of 900 gigabits can be sent back to the earth every day.[2]
On January 20, 2024, NASA successfully tested a new laser positioning system with the help of the Lunar Reconnaissance Orbiter (LRO),Laser translation can be used to locate and even track objects on the moon surface.[4]
Main tasks
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On June 23, 2009, the probe entered lunar orbit;On September 15, the probe entered the orbit 50km away from the lunar surface for high-resolution lunar surface mapping;After more than one year of observation in this orbit, the detector entered a higher orbit in October 2010 to carry out an expanded scientific mission, which is expected to last for five years.[3]
The probe also carried a secondary payload, the Lunar Crater Observation and Sensing Satellite (LCROSS)“Centaur”The upper level consists of two parts.The upper stage of Centaurus is actually an impactor whose mission is to hit the south pole of the moon.In addition to the detailed observation of the impact process when the upper stage of Centaurus impacts the moon, the mission of the "Watch Spacecraft" also includes acting as another impactor to impact the moon for the second time. One hour after launch, the LCROSS and the detector will be separated and fly to the moon along their respective scheduled tracks.On October 9, 2009, LCROSS reached the south pole of the moon, and the upper stage of Centaurus was separated from the "watch spacecraft".A few hours later, the upper stage of "Centaurus" hit a crater at the south pole of the moon at a speed of 2.5 km/s at an angle of 75 ° with the lunar surface, and the smoke and dust generated by the impact continued to spread outward.At this time, the "Watch Spacecraft" flew over the smoke, and the instruments it carried measured and analyzed the smoke, searching for water information.Fifteen minutes after the upper stage of Centaurus hit the moon, the "Watch Spacecraft" also hit the moon and sent the collected data back to the Earth before crashing.[3]
Main performance parameters
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The emission mass of the detector is 1846kg, and the dry mass is 949kg.The main platform is a cuboid structure with a size of 3.8m × 2.6m × 2.7m.The detector adopts a modular structure, mainly including propulsion system module, electronic system module and payload module. The main propulsion adopts a bipropellant propulsion system, and the unit hydrazine thruster is used for attitude control.Three axis stabilization is adopted. The attitude control system includes two star sensors, one inertial measurement unit, four reaction momentum wheels and a unit hydrazine thruster.The power supply system adopts 1850W solar wing (with an area of 10.7mtwo）The communication with 80A · h lithium-ion battery adopts S and Ka frequency bands, where the low speed uplink/downlink data rate of S frequency band is 2.186 Mbit/s, and the high-speed downlink data rate of Ka frequency band is 100~300 Mbit/s, includingCosmic ray telescope, Lunar Exploration Neutron Detector, Diviner Lunar Radiometer, Orbiter Laser Photometer, Lehmann Alpha Surveyor, Orbiter Camera, Small S-band and X-band Synthetic Aperture Radar.[3]
LCROSS“Centaur”The upper stage has a mass of 2000kg, the "Watch Spacecraft" has a mass of 534kg, and the hydrazine fuel 300kg propulsion system includes two groups of eight unit hydrazine thrusters.The power system adopts 420W body mounted solar array and 40A · h lithium ionBattery pack。S-band system is adopted for communication, including two omnidirectional antennas and two horn antennas.Payload includes 2 visible light cameras, 3Infrared camera3 setsa spectrometerAnd 1 setPhotometer。[3]
Payload
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The LRO carries six main instruments and equipment.
Lunar Orbiter Laser Altimeter (LOLA)The instrument, developed by Goddard Space Flight Center in Maryland, can provide high-precision digital elevation maps of the moon. These maps can be used to locate the landing point of the robot lunar lander when landing on the moon from 2010 to 2011.
LOLA can divide a single laser pulse into five beams, and then determine the distance by measuring the time difference between different beams emitted by the moon surface.LOLA can also cover the moon surface by laser beam to measure the fluctuation of the moon surface, measure the emissivity of the moon surface by the intensity of the transmitted energy, and measure the slope of the moon surface by the different return times of the laser beam.[2]
After obtaining the digital elevation map of the moon surface, the distribution of permanent shadow area and permanent light area on the moon surface can be determined.
Lunar Reconnaissance Orbiter Camera (LROC)The instrument is used in conjunction with LOLA and consists of a narrow angle camera and a wide angle camera.The narrow angle camera can obtain panchromatic images with a resolution of 50 cm, which is enough to see the landing site of the Apollo spacecraft and the spacecraft parked on the moon surface.When LRO flies in lunar orbit, narrow angle camera will only be used 5 to 10 times in each orbit.The wide-angle camera can provide panoramic images of the moon at seven wavelengths with a resolution of 100 meters to describe the mineral composition of the moon surface.[2]
The LRO's orbit allows it to cross the lunar poles 10 times a day at a height of 50km, in order to obtain images of areas of greatest interest to scientists and astronauts.The high-resolution digital map can guide the robot login and the subsequent manned login to the most promising areas where ice and solar energy exist at the same time.For example, moving images of the polar regions of the moon to help understand the lighting patterns of a particular season.
Lunar surveyNeutron detector(LEND) This instrument is used together with the multispectral wide-angle camera to detect the composition of the moon surface, and is used to measure the neutrons emitted by the lunar surface material under cosmic ray irradiation.Hydrogen can absorb neutrons, so the "neutron reflectivity" can be measured to determine whether there is hydrogen in a certain state on some components of the moon surface.[2]
The polar regions of the moon are rich in hydrogen - probably ice left by comet collisions in the early history of the moon.The resolution of LEND is 10km, which can check whether there is water at the most likely position in the permanent shadow area of the moon surface.
Multichannel solar emissivity and infrared filtered radiometer (DIVINER)The instrument is used together with LEND to measure the temperature of the moon surface.It can help locate cold and depressed areas covered by shaded areas where ice may exist.Generally, ice is most likely to exist in areas with temperatures below 50K.
Lehmann Alpha Project Instrument (LAMP)This instrument is also used to search for ice. In fact, it is the same instrument installed on the ESA Comet Rosetta detector launched in 2004.By using ultraviolet light from stars, LAMP can find ice on the dark surface of deep pits in the polar regions of the moon.[2]
radiation effect Cosmic ray telescope(CRaTER) This instrument is the last major instrument on LRO. It can measure the radiation environment that future astronauts will face and describe the radiation protection that astronauts need for safety reasons.
