IAA, June 17, 2015, Saint Petersburg, Russia Lunar Laser Ranging: History and current status Jean-Marie Torre, Université de Nice Sophia-Antipolis, Centre National de la Recherche Scientifique (UMR 7329), Observatoire de la Côte d’Azur, Géoazur, 2130 route de l’observatoire, Caussols, France

Overview of this talk 1.History of the measurement of the Earth- Moon distance 2.The Lunar Laser Ranging 3.History of the USSR-France cooperation 4.The LLR stations around the world 5.The future and conclusions IAA, June 17, 2015, Saint Petersburg, Russia

1. History of the measurement of the distance of the Moon Lunar eclipse method: –Aristarchus of Samos, Hipparchus, 310 – 120 before JC Lunar parallax method –Lalande and La Caille (1751) RAdio Detection And Ranging, Lunar Laser Ranging (LLR), since 1969 IAA, June 17, 2015, Saint Petersburg, Russia

1. Mean distance of the Moon Aristarchus km Hipparchus km RADAR km Lunar Laser xxxxxx km

IAA, June 17, 2015, Saint Petersburg, Russia 1. Radar measurements ( RAdio Detection And Ranging ) First measurements in 1957 –Precision of 6 km Measurements from 1959 to 1960 –Precision of 2 km Difficulties et limits –Uncertainty on the propagation of radio waves in the atmosphere –Difficulty to synchronize the pulses –Uncertainty of the measurement zone –Uncertainty of the duration of the radar pulse

Overview of this talk 1.History of the measurement of the Earth- Moon distance 2.The Lunar Laser Ranging 3.History of the USSR-France cooperation 4.The LLR stations around the world 5.The future and conclusions IAA, June 17, 2015, Saint Petersburg, Russia

2. History and principle of the LLR End of 50s : Princeton, R. H. Dicke proposed: –To use the Moon (dense and distant body) to measure the variation of the gravitational constant –To light the Moon and compare the position of the spot on the Moon with the position of stars 1960 : Pulsed ruby laser 1961 : Reduction of the pulse width, Q-switch 1962 : Princeton, J. E. Faller proposed –To use the Ranger missions to drop reflectors

IAA, June 17, 2015, Saint Petersburg, Russia 2. History of the LLR 1962 : –M.I.T., L. D. Smullin et G. Fiocco, observation of reflections on the Moon using a milliseconds pulsed laser –Crimea Astrophysics Observatory, Graszuk et al. And Kokurin report results with Q-switch ruby lasers 1963 : –H. H. Plotkin proposed to drop reflectors on the Moon

IAA, June 17, 2015, Saint Petersburg, Russia 2. Lunar Laser Telemetry Is the measurement of round-trip times of laser pulses from a transmitter (ground station) and a target (reflector) This requires: –A target: The reflector –A light source: The laser –Optics: The telescope –An instrument for measuring the time of flight: event timer or chronometer

IAA, June 17, 2015, Saint Petersburg, Russia 2. Reflectors Difficulties –Speed aberration: The station moved between the time of the emission and the return of the light (1.5 to 2 km). The maximum size is 12 cm –The lunar surface temperature variations (+120°C to -180°C). Fused silica –Libration more than 11° Choices –American reflectors : 100 to 300, 3.8cm –French reflectors : 14, 10.6cm

IAA, June 17, 2015, Saint Petersburg, Russia 2. APOLLO missions APOLLO XI (07/1969) Square of 46 X 46 cm 100 corner cubes APOLLO XIV (02/1971) Square of 46 X 46 cm 100 corner cubes APOLLO XV (07/1971) Rectangle of 104 X 61 cm 300 corner cubes

IAA, June 17, 2015, Saint Petersburg, Russia 2. LUNA 17 et 21 missions Lunokhod 1 (11/1970) Lunokhod 2 (01/1973) 14 corner cubes, 44 X 19 cm

IAA, June 17, 2015, Saint Petersburg, Russia 2. Reflectors location

IAA, June 17, 2015, Saint Petersburg, Russia 2. Apollo 11 and 14

IAA, June 17, 2015, Saint Petersburg, Russia 2. Apollo 15

IAA, June 17, 2015, Saint Petersburg, Russia Lunokhod 1 et 2

IAA, June 17, 2015, Saint Petersburg, Russia 2. French LLR station (Grasse) –Telescope diameter :1.54 m –Elevation : 1270 m –Laser : Nd-YAG frequency-doubled 532nm 70 ps pulse width 200 mJ in green 10 Hz pulse rate –Detection : APD in Single photon mode –Timing : Sub-picosecond event timer

IAA, June 17, 2015, Saint Petersburg, Russia 2. Lasers Ruby lasers (from 1981 to 1986): –Wave length : nm (red) –Pulse width : 3 ns –Energy per pulse : 3 J –Cadence : 1 shoots each 6 seconds Nd-YAG lasers (since 1986) : –Wave length : 1064 nm (IR), doubled : 532 nm (green) –Pulse width : 70 ps –Energy per pulse : 200 mJ –Cadence : 10 shoots per second

IAA, June 17, 2015, Saint Petersburg, Russia 2. Lunar Laser Ranging station (Grasse)

IAA, June 17, 2015, Saint Petersburg, Russia 2. Lunar-laser telemetry Project initiated in France in 1965 (GRGS) –Same problems than with the radar –Better precision : few hundred meters United States propose to place reflectors on the Moon (LuRE) –APOLLO 11, 14 et 15 missions Cooperation CNES-INTERCOSMOS –LUNA 17 et 21 missions

IAA, June 17, 2015, Saint Petersburg, Russia 2. First results August 1969, first echoes at the Lick Observatory (USA) In 1969 and 1970, Mc Donald (USA), Catalina Mountain (USA), Pic du Midi (France), Simeiz (Crimea, USSR), Japan, Haleakala (Hawaii, USA), Australia

Overview of this talk 1.History of the measurement of the Earth- Moon distance 2.The Lunar Laser Ranging 3.History of the USSR-France cooperation 4.The LLR stations around the world 5.The future and conclusions IAA, June 17, 2015, Saint Petersburg, Russia

3. History, USSR-France cooperation 1967 : 3 techniques are used in space geodesy –Photography on stars background with the Echo satellites and Pageos –Transit Doppler measurements on satellites –Laser telemetry on Beacon et Diadème satellites During the cold war, the cooperation will be limited to: –The photography –The Lunar Laser Telemetry

IAA, June 17, 2015, Saint Petersburg, Russia 3. History, USSR-France cooperation Professor Basov (Nobel Price of physique in 1964) proposes a French-Russian cooperation on the making of reflectors 1968 : Meeting in Moscow (Basov, Kokurin and Husson) determines the size based on a study of Sud Aviation –Labedev Institute works without success on hollow reflectors –Sud Aviation chooses reflectors giving satisfaction. It is already manufacturer of satellite reflectors D1 –The orientation is left out. Only by the end of mission that the vehicle is stopped towards the Earth.

IAA, June 17, 2015, Saint Petersburg, Russia 3. Lunokhod 1 lunar mission On November 17, 1970, the Luna 17 automated station soft-landed on the Moon near the Mare Imbrium, at a point 50 km to the south of Cape Heraclides. This station carried a roving vehicle called Lunokhod 1. Weighing 750 kg on Earth, it was self-propelling and carried scientific instruments in a hermetically sealed, temperature controlled container. It also included French laser reflectors for studying the Moon’s movements. The reflector panel, made up of 14 corner cubes prisms and protected by a cover, was situated on an extendible device towards the front of the vehicle. Active operations went on with this vehicle over a period of 7 lunar days, coming to an end on June 17, 1971; this vehicle ran on solar charged batteries and could not therefore move during lunar nights.

IAA, June 17, 2015, Saint Petersburg, Russia 3. Lunokhod 1 lunar mission

IAA, June 17, 2015, Saint Petersburg, Russia 3. Observation campaigns The first echoes from this reflector were obtained on the night of 5-6 December A ruby laser had been set on a one meter diameter telescope in the Pic du Midi Observatory. Then the Lunokhod vehicle moved on. It came to its final stop on a site situated around 2.3 km north of its point of landing.

IAA, June 17, 2015, Saint Petersburg, Russia 3. Lunar laser telemetry in the CERGA During the first few years of observations, the strategy consisted of concentrating on the reflector placed by Apollo 15 which had a higher quality output and was easier to locate. Like all reflectors placed by the Apollo missions, there was little loss of signal during low lunar lighting conditions. Tests were successfully carried out on the reflector on the second Russian lunar vehicle Lunokhod 2. At the time, the need to have measurements rapidly led to the decision to abandon laser emissions to the Lunokhod 1 reflector.

IAA, June 17, 2015, Saint Petersburg, Russia 3. Tracking campaign In 2003, P.J. Stooke from the University of Western Ontario (Canada), using Clementine orbiter images and Soviet mapping, proposed a new location. J. Williams calculated a new set of coordinates and proposed a new campaign. The bad weather during the campaign didn't permit to obtain any return.

IAA, June 17, 2015, Saint Petersburg, Russia 3. Lunokhod 1 has been found On June 18, 2009 NASA launched a lunar satellite LRO (Lunar Reconnaissance Orbiter) into polar orbit on 23 June at an altitude of 50 km. Thanks to its high resolution camera, the surface of the Moon could be explored and the search began for Lunokhod 1. In March 2010 an American team led by Mark Robinson from the University of Arizona succeeded in detecting Lunokhod 1 and deduced the coordinates of Lunokhod to within 100 m. On April 22, 2010, Professor Tom Murphy’s team (Apache Point Observatory Lunar Laser-ranging Operation) obtained laser echoes from the Lunokhod 1 reflector. In October, the McDonald station (USA) obtained echoes. In April 2013 the Grasse Observatory also obtained echoes.

IAA, June 17, 2015, Saint Petersburg, Russia 3. Lunokhod 1 déplacement et LRO image

Overview of this talk 1.History of the measurement of the Earth- Moon distance 2.The Lunar Laser Ranging 3.History of the USSR-France cooperation 4.The LLR stations around the world 5.The future and conclusions IAA, June 17, 2015, Saint Petersburg, Russia

4. LLR stations McDonald (Texas, USA) since 1969 Grasse (France) since 1981 Wettzell (Germany) Matera (Italy) since 2003 Apache Point (New Mexico, USA) since 2005

IAA, June 17, 2015, Saint Petersburg, Russia McDonald, Texas, USA MLRS Telescope: 0.75 m Elevation: 2006 m

IAA, June 17, 2015, Saint Petersburg, Russia Grasse, France MéO Telescope: 1.5 m Elevation: 1270 m

IAA, June 17, 2015, Saint Petersburg, Russia Apache Point, New Mexico, USA APOLLO Telescope: 3.5 m Elevation: 2800 m

IAA, June 17, 2015, Saint Petersburg, Russia Wettzell, Allemagne WTLRS Telescope: 0.75 m Elevation: 665 m

IAA, June 17, 2015, Saint Petersburg, Russia Matera, Italie MLRO Telescope: 1.5 m Elevation: 537 m

IAA, June 17, 2015, Saint Petersburg, Russia 4. LLR Data Report Card

4. Results by station in 2013 IAA, June 17, 2015, Saint Petersburg, Russia

4. Distribution of Normal Points with the age of the Moon

4. LLR : Paris Observatory Lunar Analysis Center POLAC (Paris Observatory Lunar Analysis Center) is one of the four lunar analysis centers of the International Laser Ranging Service. It is located at SyRTE laboratory of “Observatoire de Paris” (France). This center works in close cooperation with the observers of the MéO Laser station (Calern, France), with the EOP and ICRS products centers of the International Earth Rotation Service and with the group in charge of the development of INPOP planetary ephemeris. IAA, June 17, 2015, Saint Petersburg, Russia

4. IAA, June 17, 2015, Saint Petersburg, Russia

4. LLR data Prediction and Validation tools Since 2010, they have developed two tools usable on-line on the web to assist LLR observers. The first tool allows to compute predictions of topocentric and geocentric coordinates of lunar targets (as retro- reflectors or craters) and predictions of round-trip times of laser-pulses between terrestrial stations and lunar retro-reflectors. The second tool allows observers to compute differences between their LLR observations and different “LLR models” IAA, June 17, 2015, Saint Petersburg, Russia

4. Prediction Tool IAA, June 17, 2015, Saint Petersburg, Russia

4. Validation Tool IAA, June 17, 2015, Saint Petersburg, Russia

4. Resulting LLR data sets ftp://polac.obspm.fr/pub/1_llr_analysis/2_llr_residuals/observations ftp://polac.obspm.fr/pub/1_llr_analysis/2_llr_residuals/observations TOTALOBS6913: Nps. All valid LLR observations (20/08/1969 – 20/05/2013). OMCD6985: 3604 NPs made by McDonald station (20/08/1969 – 30/06/1985). OMCD8388: 631 NPs made by McDonald station (02/08/1983 – 27/01/1988). OMCD8813: 3653 NPs made by McDonald station (29/02/1988 – 20/03/2013). OGRA8486: 1188 NPs made by Grasse station (07/04/1984 – 12/06/1986). OGRA8705: 8324 NPs made by Grasse station (22/01/1987 – 30/07/2005). OGRA0913: 654 NPs made by Grasse station (11/11/2009 – 20/05/2013). OHAL8490: 770 NPs made by Haleakala station (13/11/1984 – 30/08/1990). OMAT0313: 83 NPs made by Matera station (22/02/2003 – 05/03/2013). OAPO0612: 1564 NPs made by APOLLO station (07/04/2006 – 28/08/2012). IAA, June 17, 2015, Saint Petersburg, Russia

Overview of this talk 1.History of the measurement of the Earth- Moon distance 2.The Lunar Laser Ranging 3.History of the USSR-France cooperation 4.The LLR stations around the world 5.The future and conclusions IAA, June 17, 2015, Saint Petersburg, Russia

5. Stations on development Hartebeesthoek, South Africa Japan China Altay, Russia

IAA, June 17, 2015, Saint Petersburg, Russia 5. Improvements in Moon dynamical and internal parameter estimations obtained by including simulated Southern Hemisphere observations (with a simulated accuracy of 2 cm) and 3.6m Southern Hemisphere observations (with a simulated accuracy of 0.5 cm)

IAA, June 17, 2015, Saint Petersburg, Russia 5. Infrared detection Positive points: –More powerful laser –Better transparency of the sky –Less noise Negative points: –Lower accuracy –More important dark noise

Information about Lunokhod The first Lunokhod was launched the February 19, 1969 but the Proton launcher disintegrated 51 seconds after the takeoff. Lunokhod 3 should have been launched in 1977 but the mission was canceled for budgetary reasons. IAA, June 17, 2015, Saint Petersburg, Russia

Conclusions Some new stations are on development The technology exits and allows to “easily” build new LLR stations They are new projects to drop other reflectors on the Moon: –Better precision –Better distribution on the Moon IAA, June 17, 2015, Saint Petersburg, Russia

Спасибо !!!