LIST OF ABSTRACTS

Session 6: "Lunar and Interplanetary Laser Ranging"

Earth Orientation Parameters from Lunar Laser Ranging

Liliane Biskupek, Jürgen Müller
Institut fur Erdmessung, Leibnitz Universitat Hannover, Germany
E-mail: biskupek@mbox.ife.uni-hannover.de

Lunar Laser Ranging (LLR) is carried out for more than 38 years. Several parameters of the Earth-Moon system can be fitted in a global adjustment with high accuracy. Here, we focus on the Earth orientation parameters (EOP).
In the global adjustment long-term lunisolar nutation coefficients for different periods (18.6, 9, 1 years) are determined and compared with results from studies of other analysis centers and values of the MHB2000 model of Mathews et al. (2002).
Furthermore, the post-fit residuals of the global adjustment are investigated by the daily decomposition method to study variations in Earth rotation UT1 and latitude VOL. In the recent LLR analysis, also different EOP series are applied as input and their effect on the Earth-Moon parameters is investigated. These results are presented.

LR-LRO Data Flow and Scheduling Operations

Christopher Clarke(1), Julie Horvath(1),Jan McGarry(2), Thomas Zagwodzki(2), Carey Noll(2), David Carter(2), Mark Torrence(3), Greg Neumann(1)
(1) Honeywell Technology Solutions Inc.
(2) NASA, Goddard Space Flight Center
(3) SGT Incorporated
E-mail: christopher.clarke@honeywell.com

The Lunar Reconnaissance Orbiter (LRO), soon to be launched in early 2009, will present new challenges to the NASA and ILRS communities, by adding new requirements for scheduling, data format, and data flow. These new requirements are necessary to help ensure the success of the on-board Lunar Orbiter Laser Altimeter (LOLA) payload instrument. The NGSLR and other approved ILRS sites will conduct one-way ranging to the lunar-orbiting spacecraft to meet the intensive orbit determination requirements needed to develop a new lunar gravity field. NASA and HTSI have coordinated with the LR-LRO mission and LOLA payload experiment team to establish new processes to meet the new data operations and data requirements. This paper will detail the coordination efforts for all LR-LRO scheduling activities for the approved ILRS sites, the coordination of all LR-LRO fire data reception at the HTSI Data Operations Facility, and all LR-LRO data delivery to NASA's CDDIS and LOLA Science Operations Center (SOC).

Status of the LLRRA21/MoonLIGHT NASA LSSO project

D. G. Currie, S. Dell'Agnello, G. O. Delle Monache, R. Vittori et al
University Maryland at CP, USA, INFN-LNF, Italy
E-mail: currie@umd.edu , simone.dellagnello@lnf.infn.it

We present the status of the MoonLIGHT/LLRRA21 project of the NASA LSSO (Lunar Sortie Scientific Opportunities) program. This approved project was presented for the call "Suitcase science to the Moon". The goals is the design, construction, modeling and full thermal and optical characterization at the INFN-LNF SCF of a laser retro-reflector array for high-accuracy 2nd generation lunar laser ranging (LLR) flight model. The ultimate goal is to reach a factor 100 improvement on current LLR.
We describe the wide breadth of physics measurements that will be possible with this new array and we report about the construction and the test of the flight model at INFN-LNF.

We also present MAGIA, a mission selected by ASI for Phase A study for the planetology science and fundamental physics measurements: Gravitational Redshift; Precursor test of Proposal MoonLIGHT/LLRRA-21 (NASA LSSO).

We also describe the design of an interplanetary CCR array for the proposed Deep Space Gravity Probe mission led by S. Turyshev of JPL. Its goas is the precise measurement of the Pioneer Effect/Anomaly in the Solar System.

Millimeter Laser Ranging to the Moon: a comprehensive theoretical model for advanced data analysis

Sergei Kopeikin
Department of Physics and Astronomy University of Missouri-Columbia
E-mail : kopeikins@missouri.edu

Lunar Laser Ranging (LLR) measurements are crucial for advanced exploration of the evolutionary history of the lunar orbit, the laws of fundamental gravitational physics, selenophysics and geophysics as well as for future human missions to the Moon. Current LLR technique measures distance to the Moon with a precision approaching 1 millimeter that strongly demands further significant improvement of the theoretical model of the orbital and rotational dynamics of the Earth-Moon system. This model should inevitably be based on the theory of general relativity, fully incorporate the relevant geophysical/selenophysical processes and rely upon the most recent IAU standards.
This talk discusses new methods and approaches in developing such a mathematical model. The model takes into account all classic and relativistic effects in the orbital and rotational motion of the Moon and Earth at the millimeter-range level. It utilizes the IAU 2000 resolutions on reference frames and demonstrates how to eliminate from the data analysis all spurious, coordinate-dependent relativistic effects playing no role in elenophysics/geophysics. The new model is based on the locally-inertial geocentric coordinates and is independent from the currently used LLR code that is written in the barycentric coordinates. The new theory and the millimeter LLR will give us the opportunity to perform the most precise fundamental test of general relativity in the solar system in robust and physically-adequate way.

Pre-Launch Testing of NGSLR Ranging to LRO

Anthony Mallama (1), Jan McGarry (2), Tom Zagwodzki (2) and Jack Cheek (1)
(1)Raytheon Information Solutions, (2) NASA Goddard Space Flight Center, USA
E-mail: anthony.mallama@gmail.com

NASA's prototype Next Generation SLR system (NGSLR) will be used for one-way ranging to the Lunar Reconnaissance Orbiter (LRO) spacecraft. The goal of this tracking is to provide an improved lunar gravity field and a precise LRO orbit. Data from the Lunar Orbiter Laser Altimeter (LOLA) instrument can then be referenced to the orbit to facilitate high accuracy surface mapping.
NGSLR has a 28 Hz, 50 milli-Joule laser for tracking LRO, in addition to the 2000 Hz eye-safe laser for Earth orbiting satellites. The laser ranging telescope is mounted on the high gain antenna which normally points toward the Earth. A fiber optic bundle carries light from the ranging telescope to the LOLA receiver. Meanwhile, the telescope for altimetry points to nadir, and thus the receiver can be used for altimetry and ranging. The 28 Hz LOLA duty cycle has separate time windows for receiving lunar reflected pulses from its own laser and Earth pulses. Thus, one testing criteria is that NGSLR pulses will arrive at LRO during the 8 milli-second Earth window.
The overall testing program for NGSLR has 137 elements including 19 that pertain specifically to tracking LRO. The following functional level test categories were derived from LRO mission requirements.
(1) The telescope must accurately point to the LRO spacecraft
(2) LRO must be scheduled as the highest priority target
(3) NGSLR software is correctly modified for LRO
(4) Laser fire is correctly controlled and measured
Each of the 19 LRO tests falls into to one of the functional categories listed above and each includes a set of criteria for success. Testing procedures involve operating the NGSLR system, running test scenarios, and comparing logged data with expected results. Interplanetary calculations make use of SPICE software, ephemeris kernels and clock files. Simulation is being used in order to complete the test program before the spacecraft is launched.
The following tests will be described. First, the arrival time of laser pulses during the Earth window will be demonstrated using SPICE calculations. Next, results of manually controlling the laser fire offset and frequency will be shown. Finally, correct and accurate telescope pointing will be illustrated with photographic images of the Moon taken through the NGSLR telescope.

Laser Ranging to the Lunar Reconnaissance Orbiter: a Global Network Effort

Jan McGarry¹, Thomas Zagwodzki¹, Ronald Zellar¹, Mark Torrence², Julie Horvath³, Christopher Clarke³, Donald Patterson³,
John Cheek⁴, Randall Ricklefs⁵, Anthony Mallama⁴, Carey Noll¹, Mike Pearlman⁶, Greg Neumann¹
1 NASA Goddard Space Flight Center
2 SGT Incorporated
3 Honeywell Technology Solutions Incorporated
4 Raytheon Information Solutions
5 University of Texas at Austin
6 Harvard-Smithsonian Center for Astrophysics
E-mail: Jan.McGarry@nasa.gov

The Lunar Reconnaissance Orbiter (LRO) will launch in early 2009 carrying multiple instruments for lunar study including the NASA Goddard Space Flight Center built Lunar Orbiter Laser Altimeter (LOLA). Also part of the mission will be the Laser Ranging (LR) instrument, which consists of a 2 cm aperture receive telescope mounted on the High Gain Antenna and a fiber optic bundle from this aperture to one of the LOLA detectors. Laser Ranging to LRO is an uplink-only measurement where ground stations time-tag their laser fires and LOLA measures the receive times to better than centimeter precision. This information will be used to improve the orbital knowledge which in turn will support the lunar gravity model development. While NASA's Next Generation Laser Ranging System (NGSLR) is the primary ground station for LR, multiple ILRS stations will also be supporting this historic mission, providing much better coverage than a single station could provide. Data from all of the participating ILRS stations will be sent to the LOLA Science Operations Center (LOLA-SOC) where ground fire events will be matched with LOLA events and ranges produced.
Coordination of the global effort will be at the Goddard Space Flight Center, where predictions and schedules will be created, data archived (CDDIS), and an LR science product generated (LOLA-SOC).
We will present the status of the preparations for global LR support, and give an overview of the scheduling, data-transfer, and real-time LR website feedback from the spacecraft.

APOLLO: One-millimeter Lunar Laser Ranging

T. W. Murphy, E. G. Adelberger, J. B. R. Battat, C. D. Hoyle, R. J. McMillan, E. L.  Michelsen, C. W. Stubbs, and H. E. Swanson,
University of California, San Diego, USA,
E-mail : tmurphy@physics.ucsd.edu

The Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) represents a recent effort in lunar laser ranging to advance our understanding of gravitational physics phenomena. APOLLO began acquiring science quality data in April 2006, and began its steady-state campaign in October 2006. In this time, we have produced about 500 normal points, with a median estimated precision of 1.8 mm. We routinely gather range information on three or four reflectors within a one-hour block of time spaced a few nights apart. We very clearly resolve the libration-induced temporal spread from the reflector arrays, and also confront issues of first-photon bias given the strong signal rate-sometimes in excess of one photon per pulse, distributed across our 4x4 avalanche photodiode array. Model residuals indicate a coherence to APOLLO data consistent with the estimated errors, exposed by the routine sampling of multiple reflectors within a short period of time. The overall scatter of the model residuals, at about 1 cm over a two-year arc, do not yet match the estimated errors, indicating either mis-estimated errors or as-yet unmodeled effects.

LRO Operations at the MLRS

Jerry R. Wiant, Randall L. Ricklefs, Peter J. Shelus
Center for Space Research & McDonald Observatory The University of Texas at Austin, USA
E-mail : jrw@astro.as.utexas.edu

The University of Texas at Austin's McDonald Laser Ranging Station (MLRS) is one of the first stations that is slated to participate in a one-way ranging experiment with the Lunar Reconnaissance Orbiter (LRO) early in 2009. The experiment will entail the laser illumination of the LRO spacecraft by the MLRS and making precise and accurate time of fire measurements. This poses several interesting challenges that involve pointing, tracking, data format definitions, and unique operational procedures. Some heretofore unanswered questions concerning the MLRS telescope beam divergence and tracking stability must be answered. The newly defined ILRS Consolidated laser Ranging Data (CRD) format will be implemented and tested, and procedures will be established to insure proper handling of LRO schedules, predictions, processing and data distribution.

NASA NGSLR Precise (~ 1ns) Transmit Epoch Timing to On-Station Time Reference for LRO Transponder Support

Thomas Varghese (1), Jan McGarry (2), Thomas Zagwodzki (2)
(1) Cybioms Corporation, Rockville, Maryland USA
(2) NASA Goddard Space Flight Center, Greenbelt, Maryland USA

The LRO transponder measurement requires the participating ranging stations to time tag the data to the station very accurately and peg the timing measurements to a stable clock that has excellent short term stability of <5 ns over the lunar orbit period of ~1 hour. The latter capability is achieved using a free running Cesium clock that has demonstrated excellent short term stability. This paper highlights the accurate time tagging to better than 1 ns to the station 1pps timing standard. For LRO transponder measurements, NGSLR uses a multimode, 50 mJ, q-switched laser that has a pulse width of 5.5 ns. NGSLR uses a standard high speed photodiode for its START detection and a Quad MCP-PMT based single photoelectron threshold receiver system for its STOP detection with a single photoelectron jitter of ~30 ps. However, the use of the above laser results in a significantly larger (>1ns) 1-σ for all timing measurements performed with this STOP receiver. Furthermore, Quad MCP-PMT at the high gain setting is extremely sensitive to large photon flux with adverse impact on its lifetime. We have devised a technique to precisely measure the timing and time tagging using the START photodiode as the common detector. Using this technique, measurements done on the external target can be transferred to an internal target for routine performance monitoring. This technique allows the operator to monitor the station performance during the 1-way ranging and ensure that the on-station time tagging is performing smoothly through the real-time internal calibration performance monitoring. The NGSLR had multiple path ways for performing the time tagging measurement; although both gave stable results within the error budget, the new pathway that was laid out was superior to the existing one as it provided a single stable unambiguous Transmit-Receive reference point for the eye-safe kilohertz laser and the high energy LRO laser. These measurements show that accurate sub-nanosecond time tagging is possible and the primary limitation is strictly the short term stability of the clock over the time interval of interest for the transponder. Details of the technique and the results are included.

The poster can be viewed at http://lrolr.gsfc.nasa.gov/lrolr_pubs.html.

The contribution of LLR data to the estimation of the celestial pole coordinates

Wassila Zerhouni, Nicole Capitaine, Gerard Francou
Observatoire de Paris - SYRTE, France
E-mail: wassila.zerhouni@obspm.fr

Poster:
This presentation is focused on the use of Lunar Laser Ranging data for the determination of the Celestial Intermediate Pole (CIP). We have first calculated the residuals of LLR observations over a period of 38 years, using the IAU 2000A-2006 model of precession nutation (i.e MHB 2000 nutation of Mathews et al. 2002 and P03 precession of Capitaine et al. 2003) and the CIO based procedure. Second, we have estimated the corrections to the X, Y coordinates of the CIP based on the IAU 2000A-2006 model every 70 days. Third, we have compared the results to the VLBI celestial pole offsets.

One-Way Ranging to the Planets

Maria T. Zuber, David E. Smith
MIT, USA
E-mail: zuber@mit.edu

Often the increase in mission complexity of flying an active laser system to the planets limits the opportunities for attempting laser tracking of planetary spacecraft. The best and most accurate method is generally considered to be the transponder approach that involves active laser systems at both ends of the link. But because of the increased complexity, risk and cost of a two-way system we have been forced to consider the value of a one-way measurement in which most of the complexity and costs are at the Earth terminal, and therefore more palatable and "fixable" should issues arise. This was the choice for LRO and hence the development of the LR system which was minimal in cost and required almost no additional spacecraft resources. The advantage of "one-way" is clear for distances of several AU if the issues of precision versus accuracy can be resolved and the opportunities for flight are greater.