IOAG-15b Optical Link Study Group Final Report to IOAG John Rush (NASA) and Klaus-Juergen Schulz (ESA) June 12, 2012 1
Actions from IOAG 15 At IOAG 15 in December 2011, OLSG was assigned the following actions: • Assess a LEO scenario that includes high latitude stations, based on improved meteorological measurements, e.g., Svalbard, Alaska, Troll, McMurdo – Extrapolated in-situ meteorological measurements at high latitude stations to be commensurate with LNOT input – Concluded that a combination of Svalbard with 6 other mid-latitude stations provides 95% PDT and allows for potential migration from additional RF payload links to optical links, Svalbard was selected due to ample terrestrial communication resources • Establish contact with International Civil Aviation Organization (ICAO) with regard to aircraft global laser safety, and continue analysis of eye safety issues. – The laser safety analysis was based on the ICAO manual on lasers emitters and flight safety and the nominal ocular hazard distance was calculated for each scenario using the uplink budget • Investigate hosting of optical terminals at existing astronomical observatory sites Some preliminary investigation was done with observatories including ESO-La Silla and Keck Observatory – – Hosting of optical communication terminal was considered feasible given compatibility with existing operations • Investigate re-use of decommissioned optical telescopes as optical terminals at existing astronomical observatory sites – Recommendation that re-use of the structure and dome is favored as most decommissioned telescope would be difficult and costly to modify • Investigate hosting of optical terminals at existing laser ranging sites – Optical communications terminal are compatible with laser ranging sites, but the wide area communications at these sites are generally lacking Investigate re-use of satellite laser ranging terminals at existing laser ranging sites • 2 – Unlikely due to differences in wavelengths
Actions from IOAG 15 • Refine cost estimates for consistency for all scenarios Single Relay Deep Optical FL (Case LEO Lunar L2 L1 Space b) Percent data transmitted (PDT) 94.8% 97.4% 99.9% 98.5% 98.0% 99.0% Number of stations required to achieve PDT: 7 2 2 2 2 3 Initial Scenario Ground Investment Costs (k€): Terminal (telescope, dome, and electronics) 3,367 15,264 10,904 12,460 102,810 13,078 Aviation Safety System 2,450 700 700 700 700 1,050 Weather and Atmospheric monitoring 1,750 500 500 500 500 750 Site Facilities Investment Costs (Buildings, Power, energy, etc.) 4,650 3,120 1,953 1,953 6,230 4,288 Wide Area Communication Investment Costs (ground communication) 2,188 157 1,242 1,242 157 1,560 Subtotal Initial Scenario Ground Investment Costs (k€) 14,405 19,741 15,299 16,855 110,397 20,726 Recurring Scenario Ground Operating Costs (k€): Site and Terminal Operating Costs 3,120 2,336 2,336 2,336 3,120 3,116 Communication Operating Costs 2,730 780 780 780 780 1,170 Subtotal Recurring Scenario Ground Operating Costs (k€) 5,850 3,116 3,116 3,116 3,900 4,286 3
Actions from IOAG 15 • Develop uplink beacon link budget for all scenarios to assess eye safety – Uplink budget was established and an eye safety assessment derived in accordance with ICAO standards Inputs LEO LEO MOON MOON L1 L1 L2 L2 MARS MARS GEO relay GEO relay Mode of operations CW CW CW CW CW CW CW CW CW CW CW CW Power [W] 0.125 0.125 10 10 70 70 50 50 555.56 555.56 2.5 2.5 Wavelength [nm] 1550 1064 1550 1064 1550 1064 1550 1064 1550 1064 1550 1064 Number of apertures 4 4 4 4 8 8 8 8 9 9 4 4 Aperture diameter [m] 0.05 0.05 0.15 0.15 0.15 0.15 0.15 0.15 0.07 0.07 0.15 0.15 Beam divergence, 1/e points [mrad] 2.79E-02 1.92E-02 9.30E-03 6.39E-03 9.30E-03 6.39E-03 9.30E-03 6.39E-03 1.99E-02 1.37E-02 9.30E-03 6.39E-03 Tx efficiency 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 MPE [W/cm^2] 0.1 0.005 0.1 0.005 0.1 0.005 0.1 0.005 0.1 0.005 0.1 0.005 ICAO Formulation NOHD slant range [m] 451 2,940 12,111 78,900 32,042 208,749 27,080 176,425 42,125 274,439 6,055 39,450 Formulation including near field NOHD slant range [m] 0 2,290 4,094 77,161 29,957 208,165 24,574 175,707 42,068 274,517 0 35,798 Irradiance at Aperture (Gauss) 4 [W/cm^ 2] 0.0127 0.0127 0.1132 0.1132 0.7922 0.7922 0.5659 0.5659 28.8716 28.8716 0.0283 0.0283
Actions from IOAG 15 • Develop uplink beacon link budget for all scenarios to assess backscattering Estimated Uplink Laser Scattered Flux from Uplink Beacon (Rayleigh scattering calculated at 1550 nm) – – Note that Aerosol scattering can vary by a decade or (up or down) depending on the site and time of day or time of year Mean Irradiance (W/m 2 ) at telescope Mean Irradiance (W/m 2 ) at telescope Mission Average Uplink due to scattered uplink laser. due to scattered uplink laser. Type Power (W) Engagement zone is 1 km away Engagement zone is 3-km away LEO 0.5 1 E-14 2.5 E-15 10 0.2 E-12 0.45 E-13 GEO Lunar 40 0.8 E-12 1.8 E-12 L1 560 1.1 E-11 0.9 E-13 L2 400 8 E-12 0.9 E-13 Mars 5000 0.8 E-10 2 E-11 5
Actions from IOAG 15 • Investigate shared use of optical relay terminals for both inter-satellite GEO-LEO links and GEO-ground feeder links. The OLSG considered sharing of optical communication relay terminals between ground and inter- – satellite to be a design optimization. However, the GEO relay case was studied further GEO-ground optical feeder link was investigated; it was found that we could provide 98% PDT with 3 – sites, assuming on-board storage 6
Actions from IOAG 15 • Investigate how IOAG Service Catalog 1 needs to be amended to include optical communications It is recommended to augment Service Catalog 1 with an optical physical, modulation – and coding sub-layer and re-use the protocol stack but this activity should not take place until the standardization process has matured – For higher data rates and re-transmission schemes, further investigation is needed and should also be considered in the standardization guidance 7
Scenario Analysis Summary Scenarios Unit LEO Lunar L1 L2 Deep Space GEO FL b) Scenario ConOps Data Volume per day Tb/d 12 5.72 7.5 7.5 1.1 216 Onboard Storage Tb 2.3 7.4 22.5 22.5 1.1 10 Data Rate per second Mb/s 10,000 622 700 700 0.7-260 10,000 CFLOS required per day h/d 0.33 2.55 3 3 1.2 6 Onboard Terminal Aperture cm 8 10 13.5 13.5 22 13.5 Tx Power W 0.5 0.5 5 5 4 2.2 Mass kg 35 30 50 50 < MRO Ka 50 Power Consumption W 120 140 160 160 < MRO Ka 160 Ground Stations Rx Terminal Size diameter m 0.4 1 1 1 12 1 Tx Apertures and Size 4x 5cm 4x 15cm 8x 15cm 8x 15cm 9x 7cm 4x 15cm Tx NOHD ICAO (1550nm) m 451 12,111 32,042 27,080 42,125 6,055 Tx NOHD Near Field (1550nm) m 0 4,094 29,957 24,574 42,068 0 Number of Terminals 7 2 2 2 2 3 PDT resulting % 94.8 97.4 98.5 99.9 99.0 98.0 8
Observations • We have narrowed the wavelength considerations to 2 wavelength regions: 1064nm and 1550nm • It was found that there are numerous techniques being investigated and demonstrated over the next few years that should lay the foundation for the standardization process Wavelength Detection, Modulation, Coding System Scenario Acquistion Downlink Uplink Downlink Uplink [nm] technique [nm] Earth Relay Inter-Satellite Link (ISL) LCT-125 ISL 1064 1064 Comm beam Coherent Coherent (DLR TerraSar-X <-> LEO-LEO uplink Detection, Detection, NFIRE 2008) Homodyne BPSK Homodyne BPSK LCT-135 ISL 1064 1064 Comm beam Coherent Coherent (ESA Alphasat 2013) LEO-GEO uplink Detection, Detection, Homodyne BPSK Homodyne BPSK LCT-135 ISL 1064 1064 Comm beam Coherent Coherent (ESA EDRS, Sentinel LEO-GEO uplink Detection, Detection, 2014) operational Homodyne BPSK Homodyne BPSK LCRD ISL 1550 1558 Beacon a) Direct a) Direct (NASA 2017) LEO-GEO detection PPM detection PPM, b) Direct b) Direct detection DPSK detection DPSK 9
Diversity of Technical Solutions Wavelength Detection, Modulation, Coding System Scenario Downlink Acquistion Downlink Uplink Uplink [nm] [nm] technique Space-Earth LCT-125 LEO-GND 1064 1064 Comm beam Coherent Coherent (DLR TerraSar-X 2009) uplink Detection, Detection, Homodyne Homodyne BPSK BPSK Optel-µ LEO-GND 1545, 1565 1064 Beacon Direct detection, PPM uplink (ESA RUAG Space 2017) OOK OSIRIS LEO-GND 1545 1560 Beacon – open OOK downlink N/A (DLR-IKN) loop LEOLINK LEO-GND 1550 C- 1568 Beacon – closed OOK downlink N/A (NASA-JPL) band loop CWDM SOTA LEO-GND 1550 and 1064 Beacon Direct detection OOK (NICT) 975 LCT-135 GEO-GND (Earth 1064 1064 Comm beam Coherent Coherent (ESA Alphasat 2013) relay Feeder Link) uplink Detection, Detection, Homodyne Homodyne BPSK BPSK LCRD GEO-GND (Earth 1550 1558 Beacon a) Direct a) Direct (NASA 2017) relay Feeder Link) detection PPM detection PPM, b) Direct b) Direct detection DPSK detection DPSK LLCD Moon-GND 1550 1558 Beacon Direct detection Direct detection (NASA 2013) photon counting PPM PPM DOT Mars-GND 1550 1030 Beacon Direct detection, Direct detection, (NASA-JPL 2018) photon counting photon counting 10 PPM PPM
Standardization and Development 11
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