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System Operations. Towards the 1-mm: A realistic goal ? A vision ? A myth ? ???. Eastbourne , October 200 5. System Operations: Accuracy. How to reach the 1 mm ACCURACY ? Is it possible ? How to reach the 1 mm STABILITY ? Is it possible ?
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System Operations • Towards the 1-mm: • A realistic goal ? • A vision ? • A myth ? • ??? Eastbourne, October 2005
System Operations: Accuracy • How to reach the 1 mm ACCURACY ? Is it possible ? • How to reach the 1 mm STABILITY ? Is it possible ? • Which developments are necessary ? Recommended ? • Is the 1 mm a realistic / achievable goal ? • Simple answer: • Yes, but we do not know WHEN Eastbourne, October 2005
1 mm: What we need … • Good LASER: SSDPL (Solid State Diode Pumped) • Short Pulse Duration: 10 ps • Good Event Timer: • A032-ET (Riga): < 10 ps RMS, < 2 ps nonlinearity, kHz ... • Dassault Modules (Graz E.T.): < 3 ps RMS, < 2 ps nonlinearity • Good detector: C-SPAD, Time Walk Compensated; • Good satellites: ZERO Signature; PLUS strong return signal ! • Grace A, Grace B, Champ: No sat signature, good signal • LARET-C: Zero signature, but weak signal Eastbourne, October 2005
1 mm: Needs a good laser … • UPGRADE THE LASER: • Switch to Solid State Lasers (e.g. kHz); • Excellent Pulse uniformity; • Excellent Stability (shot-to-shot, day-by-day); • Short Pulses (10 ps in Graz) => better accuracy; • We do not see any disadvantage ... • Change from „TUBES“ to „SOLID STATE“ !!! Eastbourne, October 2005
1 mm: Needs strong signals … • With a 10-ps laser, good ET, strong-signal / zero signature sat.: • 2 – 3 mm Single Shot RMS precision; • With VERY strong returns (> 300 pe / return): 1 mm SS RMS • Measure Return Signal Strength of EACH return: • C-SPAD: Use Time Difference Comp. / Uncomp. Output • Select returns with > 300 pe only 1 mm RMS • In CALs to 4 km Retro Target: Routinely achieved; • Current project ongoing in Graz; results in Canberra expected October 2005
CAL RMS: From 10 Hz to kHz Eastbourne, October 2005
CAL P-M: From 10 Hz to kHz Eastbourne, October 2005
1 mm with flash lamp laser ? • Old 10-Hz-Laser system in Graz (but with E.T. etc.): • Peak-minus-Mean: about ± 2 mm variations; • Too big; => difficult to reach the 1 mm goal !!! • With new Solid State Laser (kHz): • Peak-minus-Mean: MUCH better, very stable !!! • about ± 0.3 mm variations only ... Eastbourne, October 2005
1 mm: Needs a good satellite … • Use Retros / panels WITHOUT satellite signatures !!! GRACE-A GRACE-B CHAMP ??? 2-3 mm SS RMS Eastbourne, October 2005
1 mm Accuracy / Stability • All previous comparisons: • From 10 Hz Flash Lamp to 2 kHz Solid State Laser • All other Equipment: Same ... • Event Timer (Graz E.T. / Dassault Modules) • Same C-SPAD; same other equipment .... • Conclusion again: Change from „TUBES“ to „SOLID STATE“ !!! Eastbourne, October 2005
Laser Pulse Width and Accuracy • Wide range of pulse widths used in SLR: • 10 ps: Graz / kHz / Solid State Laser; • 35 –50 ps: Standard Lasers; Flash Lamp Pumped; • 110 ps: e.g. Herstmonceux Flash Lamp Pumped; • 300 ps: SLR 2000 • Any other ? • What is the „best“/„optimum“/„desired“ pulse width ? Eastbourne, October 2005
Laser Pulse Width Selection • 10 ps: Present optimum; no reason for shorter pulses … • No significant contribution to overall systematics anymore; • Excellent for Single-Photon-Detectors; • Allowa to see – and to handle - Single Retros …. • 300 ps: Can be eye-safe at e.g. 50 cm dia, if < 150 µJ / pulse • Relatively big contribution to overall systematics; • 1mm goal for Lageos => difficult with SPE signals< • Satellite signature problem slightly increasing; • Less problems with LEOs / MultiPhoton Detection Eastbourne, October 2005
MeasuringLaser Pulse Width • I have no idea how to measure it ... • But Jerry Wiant is doing it Eastbourne, October 2005