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13th International Laser Ranging
Workshop
"Toward Millimeter Accuracy"
Submitted
Abstracts
Lunar Laser Ranging (P. Shelus and J.F. Mangin)
| Title | Primary Author |
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| Recent contributions to LLR analysis | Jean Chapront |
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Paris Observatory M. Chapront-Touze and G. Francou Presented by Peter Shelus Paris Observatory Lunar Analysis Center (POLAC) has used the Lunar Laser Ranging (LLR) data provided, between 1972 and 2001, by five sites: McDonald (Texas, 3 locations), Grasse (France) and Haleakala (Hawaii). A semi analytical solution has been built for the lunar orbital motion and librations. With respect to prior solutions several improvements have been introduced in the statistical treatment of the data, nutation and libration models and the distribution of the weights of LLR observations. Globally, for recent observations, more accurate than the earlier ones, the root mean square error is within 2 to 3 centimeters in the lunar distance. Special attention has been paid to the determination of the correction to the IAU76 constant of precession and the value of the secular acceleration due to the tidal forces. The positions and velocities of the stations have also been fitted. The lunar theory ELP2000-96 is referred to a dynamical system and introduces the inertial mean ecliptic of J2000.0. The positioning of the dynamical system with respect to ICRS has been performed as well as the offsets of the Celestial Ephemeris Pole. Finally, EOP series (UT0-UTC & VOL) have been determined, between 1987 and 2001, from the LLR normal points of the 2 operational modern stations, MLRS2 and CERGA. Oral presentation; received August 8, 2002 |
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| The OCA LLR Station : An Update | Jean-Francois Mangin |
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OCA-CERGA F. Mignard, D. Feraudy, M. Furia, J.M. Torre, G. Vigouroux Presented by: Gerard Vigouroux The OCA station located in southern France shares its activities between the Moon and high-altitude satellites. Since the last laser WS several technical improvements have been studied or implemented, like a an optical device for the correction of the velocity aberration for the satellites. For the Moon we are ready to use the redundant path on the last amplifier of the laser to double the output energy at 800 mJ in 300 ps. A major maintenance on the steering of the dome has been carried out in 2002 to replace the worn-out main rail. A quality assessment has been performed on three years of range measurements on Apollo 15. The internal consistency per night is excellent, varying between 1 to 15 mm, with no obvious correlation with the number of returns, the number of normal points over each night, the pressure or the lunar libration. Smaller numbers, but with as much scatter, (0.3 to 3 mm) are obtained on the GPS satellites, but with a pulse of only 20 ps. A major effort is underway to automate the observations of the satellites to overcome the chronically under staffing of the station and at the same time increase its efficiency. In 2001, the station netted 350 normal points on the Moon and more 9500 on the high-altitude satellites. Despite the funding uncertainties and the limited staff we plan to continue the operations on the Moon in the coming years with the main objective of improving the testing of gravitation theories and the comparison of reference frames. Oral presentation; received August 8, 2002 |
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| APOLLO: Multiplexed Lunar Laser Ranging | Thomas Murphy |
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University of Washington, Department of Physics The Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) is a next-generation lunar laser ranging (LLR) campaign aimed at order-of-magnitude improvements in tests of gravitational physics via millimeter range precision. We will employ the 3.5 m telescope at the Apache Point Observatory (APO), located in southern New Mexico at an altitude of 2800 m. As a result of the large aperture size and excellent seeing conditions, APOLLO expects to detect 2--10 lunar return photon per pulse. Relative background immunity permits operation in daylight and at full moon, resulting in better sampling of the lunar orbit. We will use avalanche photodiode (APD) arrays as the detector for APOLLO, allowing multiple photons within a single return pulse to be individually time-tagged with high precision. Immediate advantages are shot-by-shot range profiles, as well as guaranteed calibration for each shot. In conjunction with a high time-precision start photodiode, one quickly builds an accurate representation of the convolved laser/detector/electronics temporal response. We describe the hierarchical, multiplexed APOLLO timing system and its implementation using commercial electronics and a programmable logic controller, as well as the various calibration procedures geared toward millimeter range precision. There is no practical limit to the number of channels employed in our timing scheme, allowing an upgrade path to larger APD array formats (10 x 10 or larger). Oral presentation; received August 21, 2002 |
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| LLR Developments at Mount Stromlo: Towards Millimeter Accuracy | Ben Greene |
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EOS John McK Luck LLR in Australia was first conducted in 1977, but there has been no LLR activity for more than a decade. The 1998 relocation of SLR effort to Mount Stromlo, a site considered unsuitable for LLR, seemed to end LLR in Australia. The recent upgrade of Mount Stromlo with high power laser tracking systems and beam processing systems for space research has allowed the feasibility of LLR to be re-considered. An experimental program of LLR is planned for late 2002, specifically to establish the operating parameters required for routine LLR operations. The objective is to obtain an operational configuration for eyesafe, millimetre-accuracy LLR from mount Stromlo. The progress of this effort will be discussed, along with elements of the technical approach. Oral presentation; received September 13, 2002 |
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Last Updated:
September 12, 2002
