1. Transponders A new Working Group in the ILRS

2. In a very general way a transponder is an active component in space Laser Beacon (synchronized to a caesium clock) Pulse Response System Asynchronous Transponders (interplanetary...) Time Transfer (T2L2) Relativity Experiments (Astrod)

3. What are transponders good for? Ordinary CCR ranging has a range dependence of The moon is realistically about the maximum distance for laser ranging as we use it today Transponder improve the link budget significantly

4. Applications of transponders Orbit Determination: Mars, Mercury, Lunar Orbiters Lunar Physics, Relativity (Lunar Lander) Optical Communications (Guide Beacons, Data Transfer) Ranging to difficult Satellites like GPS or GALILEO Time Transfer

5. Proposed and Upcoming Missions Lunar Reconnaissance Orbiter (LRO) Messenger, BepiColombo (Mercury Altimeter) T2L2, Mini-ASTROD Selene II Testbed Operations: MOLA, BELA-Demonstrator

6. Transponder Working Group Charter Preamble Presently, transponders are not used in the field of SLR and LLR. The great advantage of this technology is a considerable improvement in the link budget for lunar or deep space ranging applications. However, this comes at the expense of more technological complexity. Now that science missions requiring precise ranging and/or time transfer on an interplanetary scale are being seriously proposed, it is both appropriate and timely that the ILRS form a Working Group to consider all aspects of the transponder technique to ensure that laser ranging will play an important role in interplanetary science.... the complete Charter is on the ILRS website

7. Current working group members: John Degnan (co-chair) Werner Gurtner Georg Kirchner Jan McGarry Ivan Prochazka Randy Ricklefs Etienne Samain Ulrich Schreiber (chair) Dave Smith Yang Fumin

8. Network Implications What wavelength has to be employed? (or several) Extra hardware necessary? (H-maser, Rangegate-Generator, etc.) Special missions may require only a few stations to participate GPS / GALILEO may want many stations to participate

9. Essential Difficulty of Epoch Use ideal Clock external Trigger real world (excel.) Electronics

10. What are the next steps Overview of the currently ongoing activities (inside and outside the ILRS) Identify areas of interest for the tracking network Mission definition (Lunar, Galileo) Work towards compatibility with missions and ILRS