Invitation to Tender for Satellite Laser Ranging Telescope System

mode entails that the telescope operates otherwise autonomously but
accepts pointing and speed commands from the SLR operating
software.
3.1.3. Possible approaches for this Invitation to Tender
There are currently two fundamentally different basic approaches for
the optical systems (telescopes) used by SLR stations worldwide: 1)
the monostatic system, where the transmitted and received laser
pulses both travel on the same optical path through the main aperture,
and 2) the bistatic system where a separate smaller telescope is used
for transmitting the laser pulse and a larger main telescope for
receiving the return pulse. Both approaches are used in the satellite
laser ranging community and both have some advantages and
disadvantages. Here the basic differences between the two different
optical setups and how they relate to this Invitation to Tender are
presented. Due to several fundamental differences in the design and
operation of the SLR system between the monostatic and the bistatic
approach, some minimum requirements as well as award criteria for
technical merit and quality are specific to the approach presented in the
tender.
Regardless of the optical system approach, to minimize the
background noise the field of view of the detector should be small
(compared to FoV's of astronomical systems). The receiving optical
system should have such a focal length / aperture ratio that forms a
field of view of a square arcminute or less on the detector (the final
value is TBD between the Contracting Authority and the winning
tenderer, and somewhat dependent on the optical system).
Monostatic system
In the monostatic system, both the laser and the detector are located in
the Coudé focus of the telescope, which is located on an optical bench
in a climate controlled room (which in Metsähovi will be located on
storey below the telescope). In this setup the received and transmitted
photons are transmitted to the required direction through the same
optical path. The direction of the beams can be accomplished either
outside of the telescope at the Coudé room, or in the optical system of
the telescope. Related to this, a major challenge for monostatic kHz
system is the amount of light originating from the transmitted pulse that
is backscattered from the telescope and related optics to the detector
where it acts as noise. This is especially the case when using 2 kHz
fire rate as multiple pulses are travelling through the telescope at the
same time. As a minimum requirement (cf. Appendix 2) the tenderer
offering a monostatic system shall describe a solution for the
separation of the transmitted and received paths. This can be
accomplished with supplementary documentation and with references
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