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Facts about SLR:
- SLR provides unique and important science through its use
of passive "cannonball" geodetic satellites
- The SLR range observable is unambiguous and relatively
insensitive to tropospheric and ionospheric path delays for
precise orbit determination (POD) applications
- SLR currently supports nearly 30 international spacecraft
missions
- Although the SLR ground segment is more expensive than
most competing radio techniques (except Very Long Baseline
Interferometry, VLBI), the spacebourne component is simple,
relatively inexpensive, passive, and requires no power
- SLR operations costs can be greatly reduced (75%) through
increased reliability, standardization, automation, and maximum
utilization of commercial parts
- New technologies are available which can reduce system
complexity and cost
Technical Goals :
- Unmanned, eyesafe operation
- 24 hour laser tracking to satellites up to 22,000 Km slant
range (GPS, GLONASS, Etalon)
- One cm (1σ RMS) single shot ranging or better
- 1 mm precision normal points to LAGEOS
- Mean Time Between Failures: >4 months
- Automated two-way communications with central processor
via Internet
- Free of optical, electrical, and chemical hazards
- Reduce system replication cost to ~$1M per system
- Reduce network operations costs through standardization
and COTS technology utilization
Unique features of SLR2000:
- Totally Automated and Eyesafe Operation
- Unmanned operations
- Uses low energy microlasers (130 μJ/pulse) at
high repetition rates (2 kHz)
- Laser beam fills 40 cm transmit/receive telescope
to meet OSHA radiation standards
- No aircraft safety radars needed
- For failsafe reliability, choose passive techniques over
active where possible, e.g.,
- Eyesafe beams vs active radars
- Passive T/R switch
- Passive short pulse generation
- Sub-unity Signal-to-Noise
Ratios (SNR) during daylight operations
- Mean signal strength: <<1 photoelectron
per laser fire
- Uses Post-Detection Poisson Analysis to extract
satellite signal from noise background in real
time, center signal in range gate, and reduce gate
width
- Photon-counting quadrant detector/multichannel
receiver provides both high resolution ranging
(1 mm precision) and sub-arcsecond angular tracking
error feedback to mount
- Use medium-size telescopes (~40 cm)
- Constrains cost of optical tracking mount
- Constrains eyesafe laser energy to about 100 microjoules
at 532 nm
- Use off-the-shelf components wherever possible
- Allows rapid component replacement and "outsourcing" of
engineering support
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