OLSG Report_Final_06_05_12 - Interagency Operations Advisory ...

Optical Link Study Group (OLSG) Final Report
IOAG.T.OLSG.2012.V1
• The data rate is 10 Gb/s.
• Data are transmitted only above 20° elevation.
• An example set of nine globally located ground terminals may provide optical
communications to the satellite
From these assumptions we deduce:
• The average amount of data dumped per contact is 3 Tbit (= 5 min x 10 Gb/s).
• With 15 orbits/day, the satellite shall dump, on average, 800 Gbit per orbit (= [12
Tbit/day]/[15 orbits/day]) with a high probability. Thus, 80s (= [800 Gb/orbit]/[10
Gb/s]) of contact time per orbit is required.
Table 7 summarizes the ConOps parameters for the LEO Scenario.
Table 7: LEO Scenario Concept of Operations Parameters
LEO Scenario
Onboard Data
Collection Rate
Onboard Storage
Capacity
Hours of CFLOS
Required per Day
Data Rate used
for Link Budget
12 Tb/day 2.3 Tb 0.3 10 Gbps
3.1.2 Space Terminal
In this section, five different concepts for LEO flight terminals are presented: DLR-IKN’s
Optical Space Infrared Downlink System (OSIRIS), the DLR/Tesat Laser Communication
Terminal (LCT), the Optel-µ terminal, NASA JPL’s 10-Gb/s terminal, and the Small Optical
Transponder (SOTA) from Japan’s National Institution of Information and Communication
Technology (NICT).
The space terminal must provide the functions described in the ConOps:
• Optical head
• Communication system
• PAT system
• Onboard storage
The electro-optics box includes lasers, laser amplifiers, encoder and modulator, data
formatting and spacecraft electrical interfaces. For most LEO satellites, the laser terminal
should possess its own coarse pointing assembly (CPA), which typically takes the form of a
periscope. Additionally, a fine pointing assembly (FPA) and optical tracking sensor should
both operate with an angular error that is much smaller than the downlink beam
divergence. A point-ahead angle (PAA) around 50 µrad should be implemented.
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