Overview for Future In-Space Operations October 2013
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Transcript of Overview for Future In-Space Operations October 2013
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Bernard EdwardsChief, Communications Systems EngineerNASA Goddard Space Flight [email protected]
Overview for Future In-Space Operations
October 2013
The Laser Communications Relay Demonstration (LCRD) will demonstrate optical communications relay services between GEO and Earth over an extended period, and thereby gain the knowledge and experience base that will enable NASA to design, procure, and operate cost-effective future optical communications systems and relay networks.
LCRD is the next step in NASA eventually providing an optical communications service on the Next Generation Tracking and Data Relay Satellites
Mission Statement
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Mission Overview
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LCRD Flight Payload2 Optical Relay Terminals• 10.8 cm aperture• 0.5 W transmitterSpace Switching Unit
Table Mountain, CA White Sands, NM
LCRD Payload and Host
Spacecraft
1244 Mbps DPSK311 Mbps 16-PPM
LCRD Ground Station 215 cm transmit aperture• 20 W transmitter40 cm receive aperture
1244 Mbps DPSK311 Mbps 16-PPM
LCRD Ground Station 11 m transmit and
receive aperture• 20 W transmitter
Mission Concept• Orbit: Geosynchronous
– Longitude TBD between 162ºW to 63ºW
• 2 years mission operations• 2 operational GEO Optical Relay Terminals• 2 operational Optical Earth Terminals• Optical relay services provided
– Ability to support a LEO User
• Hosted Payload• Launch Date: Dec 2017
NASA Optical Communication Technology Strategy
Near EarthFlight Terminal
Deep Space Flight Terminal
SCaN OpticalGround Infrastructure
Near Earth Missions
LLCDLADEE Demo
Optical CommGround Stations
(LLGT, OCTL, Tenerife)
Key DOT Technology Identification
&Development
Technology Transfer
GEO Demo –LCRD
2013
Technology Investment and Development
LCRD
LEO Demo
2017 2020 2025
Commercialization
Optical Module
Controller Electronics
DPSKModem
Mini FOG
Flexured Gimbal Mount
CFLOS Analysis, Optical Comm Cross Support
PPM Laser TransmitterLow-noise laser
Spacecraft disturbance rejection platform, piezo-based point-ahead mechanism
SNSPD arrays, photon counting space receiver, ground receiver detection array, NAF APD/nanowire det., COTS quadrant spatial-acquisition detectors
SCaN Operational Optical Ground StationsAdded as Mission Needs Require
(including International Space Agency Sites)
•Stabilization
• Detectors
• Vibration
• Systems Engineering
• Laser Power/Life
• Pointing
Candidate Deep Space Host Demo Mission
Other Deep Space Missions
Commercialized
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Leveraging the Lunar Laser Communications Demonstration (LLCD)
• …• NASA’s first high rate space laser communications demonstration
• Space terminal integrated on the Lunar Atmosphere and Dust Environment Explorer (LADEE)
• Launched on 6 September 2013 from Wallops Island on Minotaur V– Completed 1 month transfer (possible lasercomm ops)– 1 month lasercomm demo @ 400,000 km
• 250 km lunar orbit– 3 months science
• 50 km orbit• 3 science Payloads
– Neutral Mass Spectrometer– UV Spectrometer– Lunar Dust Experiment
LLCD Flight Hardware
Optical Module• Designed and fabricated by MIT LL• Inertially-stabilized 2-axis gimbal• Fiber-coupled to Modem transmit (Tx) and receive
(Rx)
Controller Electronics• Built by Broad Reach Engineering for
OM, MM control• Telemetry & Command (T&C)
interface to S/C
Modem Module (MM)• Designed and fabricated by MIT LL• Pulse Position Modulation Only• Digital encoding/decoding electronics,1550 nm
fiber Tx and Rx
All Modules Interconnected via electrical cables and optical fibers
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Lunar LasercomSpace Terminal
Lunar LasercomOCTL Terminal (JPL)
Table Mtn, CA
Lunar LasercomGround Terminal
LADEE Spacecraft
1.55 um band
Lunar LasercomOptical GroundSystem (ESA)
White Sands, NM
Tenerife
DL 622 MbpsUL 20 Mbps
DL > 38 MbpsUL > 10 Mbps
DL > 38 Mbps
Modem Module
Controller Electronics
Optical Module
LCRD will leverage designs and hardware from LLCD, with modifications to satisfy mission requirements.
LLCD Provides the Foundation for LCRD
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LCRD Design Reference Mission
• Simultaneous multiple real-time user support and multiple store & forward user support multiplexed on single trunkline
• Different user services: frame, DTN, …• Scheduled and Unscheduled Ground Station handovers• Number of Users, Mission Operations Centers (MOCs),
and Payloads scalable• Emulation of different relay and user location and orbits
by the insertion of delays and disconnections in the data paths
User 1 S/C
User n S/CGS-1 GS-m
User 1 MOC User k MOC
LMOC
Active optical link
Future optical link
Terrestrial Internet ProtocolNetwork
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• Hosted on a Space Systems/Loral Commercial Communications Satellite
• Flight Payload– Two MIT LL designed Optical Modules (OM)– Two Integrated Modems that can support both
Differential Phase Shift Keying (DPSK) and Pulse Position Modulation (PPM)
– Two OM Controllers that interface with the Host S/C
– Space Switching Unit to interconnect the two Integrated Modems and perform data processing
• Two Optical Communications Ground Stations– Upgraded JPL OCTL (Table Mountain, CA)– Upgraded LLCD LLGT (White Sands, NM)
• LCRD Mission Operations Center (LMOC)– Connected to the two Optical Communications
Ground Stations– Connected to Host S/C MOC
LCRD Baseline
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LCRD GS and Optical Space Terminal Location
GEO Locations were chosen to ensure at least 20° above horizon for both Ground Stations
161W 112W 63W
OST Possible Location
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LCRD Mission Architecture
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LCRD Flight Payload
Host MissionOps Center (HMOC)
NASA GSFC
Table Mountain, CA White Sands, NM
Host SpacecraftRF Link
LCRD Payload and Host
Spacecraft
1550 nm band
LCRD Ground Station-21 @ 15 cm @ 20 W (PPM/DPSK)1 @ 40 cm (PPM/DPSK)
10 cm @ 0.5 W (PPM/DPSK)DPSK at 1.244 Gbps
PPM at 311 Mbps
NISNLCRD Ground Station-1
1 m @ 20 W (PPM/DPSK)
1550 nm band
Based on Lunar Lasercom
Ground Terminal (LLGT)
LCRD Optical Ground System (LOGS) -
OCTL
LCRD Mission Ops Center (LMOC)
NISN NISN
Chiller for cooling trailer and telescopes
Converted 40-ft ISO container housing controls, modems, and
operator console
18-ft Clamshell
weather cover
4x UL Transceivers4x DL Receivers
Environmental enclosure
surrounding UL and DL telescopes
Relay Optical Link
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Relay Link Features:• Coding/Interleaving at the link edges
o Rate ½ DVB-S2 codec (LDPC)o 1 second of interleaving for atmospheric fading
mitigation• Data can be relayed or looped back• PPM or DPSK can be chosen independently on each
leg
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Atm
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Opt
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Mod
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Mod
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Opt
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GS-1 GS-2
OST-1 OST-2
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Uni
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LCRD Payload
Bus Overview• Existing SS/L commercial satellite bus
Bus and Payload Overview
Star Tracker Star Tracker
Optical Module
Optical Module
CE CE
ModemA
Switch
ModemB
ModemA
ModemB
Radiator (back view)
Equipment Panel& Radiator
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2
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• LCRD package is located on the S/C Earth deck, similar to a typical North panel extension
• The enclosure North-facing surface is the main radiator with Optical Solar Reflectors
• Secondary LCRD radiator panel is on the South side
• Star trackers located on the top of the enclosure for optimal registration with OMs
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Payload Hardware Overview
Integrated Modem (qty 2)– 0.5 W transmitter; optically pre-amplified
receiver– DPSK and PPM modulation– 27 kg, 130 W– Supports Tx and Rx frame processing
No on-board coding and interleaving
Optical Module (qty 2)– Gimbaled telescope (elevation over azimuth)
12° half-angle Field of Regard– 10.8 cm aperture, 14 kg– Local inertial sensor stabilization
Controller Electronics (CE) (qty 2)– OM control/monitoring– Interface to Host Spacecraft– 7 kg, 151 W
Space Switching Unit (qty 1)– Flexible interconnect between modems to
support independent communication links High speed frame switching/routing
– Command and telemetry processor
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Flight Payload Functional Diagram
Space Switching Unit
Controller Electronics 1
Optical Module 1 Optical Module 2
Host S/C1553
To & From Ground or LEO Terminals
To & From Ground or LEO Terminals
fiber
Integrated Modem 2Host S/C
1553Host S/C1 PPS Host S/C
1 PPS
Transmitter Receiver
Optical Data & Frame Processing
Integrated Modem 1
TransmitterReceiver
Optical Data & Frame Processing
fiber
Frame SwitchingCommand &
Telemetry Processing
Host S/CInterface
Load Drivers
Sensor Processing
PAT Processing
Controller Electronics 1
Host S/CInterface
Load Drivers
Sensor Processing
PAT Processing
Pointing & Jitter
Control
Optical Telescope
Pointing & Jitter
Control
Optical Telescope
Analog
SpaceWire Downlink communication signal
Uplink communication signal
Uplink acquisition beacon signal
High Speed Serial
Two Ground Stations
JPL will upgrade the JPL Optical Communications Telescope Laboratory (OCTL) to form the LCRD Optical Ground Stations (LOGS)• This is a single large telescope design• Adaptive Optics and support for DPSK
will be added
LCRD will upgrade the Lunar Laser Communications Demonstration (LLCD) Ground Terminal developed by MIT Lincoln Laboratory• This is an array of small telescopes with
a photon counter for PPM• Adaptive Optics and support for DPSK
will be added
Both stations will have atmospheric monitoring capability to validate optical link performance models over a variety of atmospheric and background conditions 16
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Ground Station Components
Ground Station 1 Ground Station 2Upgrade of JPL’s OCTL Upgrade of LLGT20 W transmit power 20 W transmit power1 meter transmit/receive aperture 40 cm receive aperture; 15 cm transmit
apertureIdentical equipment for atmospheric monitoringReceive adaptive optics Receive adaptive optics and uplink tip/tilt
correctionIdentical Ground Modem, Codec, and Amplifier systems for DPSK and PPM Wide angle beacon for initial acquisition Scanning beacon for initial acquisitionLaser safety system for aircraft avoidance Operation in restricted flight airspace
Legacy array of superconducting nanowire single photon detectors
DPSK Modulation/Demodulation
DPSK Receiver
DPSK Transmitter
In the DPSK system, each slot contains an optical pulse with phase = 0 or π. Data carried as a relative phase difference between adjacent pulses.
At the DPSK receiver, the original sequence is demodulated using a fiber delay-line interferometer to compare the phase of adjacent pulses.
The average power-limited transmitter allows peak power gain for rate fall-back via “burst mode” operation.
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PPM SignalingFor PPM, the binary message is encoded in which of M=16 slots contains a signal pulse.o Optical modulation accomplished with the same hardware that implements burst-
mode DPSK, with the applied phase irrelevant for PPM
PPM Signaling
PPM Receiver
PPM demodulation is accomplished by comparing the received power in each slot with a (controllable) threshold valueo Uses the same pre-amplifier and optical filter as the DPSK receiver, but by-passes
the delay-line interferometer
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Line of Sight and CFLOS
• The first consideration in link establishment is whether a line of sight between the source and destination exists.
• Free space laser communications through Earth’s atmosphere is nearly impossible in the presence of most types of clouds.
– Typical clouds have deep optical fades and therefore it is not feasible to include enough margin in the link budget to prevent a link outage.
– Key parameter when analyzing free space laser communications through the atmosphere is the probability of a cloud-free line of sight (CFLOS) channel.
• A mitigation technique ensuring a high likelihood of a CFLOS between the source and destination is needed to maximize the transfer of data and overall availability of the network.
– Using several laser communications terminals on the relay spacecraft, each with its own dedicated ground station, to simultaneously transmit the same data to multiple locations on Earth
– A single laser communications terminal in space can utilize multiple ground stations that are geographically diverse, such that there is a high probability of CFLOS to a ground station from the spacecraft at any given point in time.
– Storing data until communications with a ground station can be initiated– Having a dual RF / laser communications systems onboard the spacecraft.
• NASA has studied various concepts and architecture for a future laser communications network. The analysis indicates ground segment solutions are possible for all scenarios, but usually require multiple, geographically diverse ground stations in view of the spacecraft.
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Network Availability
• A ground station is considered “available” for communication when it has a CFLOS at an elevation angle to the spacecraft terminal of approximately 20° or more.
• The network is “available” for communication when at least one of its sites is “available.” • Typical meteorological patterns cause the cloud cover at stations within a few hundred
kilometers of each other to be correlated. – Stations within the network should be placed far enough apart to minimize these correlations – May lead to the selection of a station that has a lower CFLOS than sites not selected, but is less
correlated with other network sites.
• Having local weather and atmospheric instrumentation at each site and making a simple cloud forecast can significantly reduce the amount of time the space laser communications terminal requires to re-point and acquire with a new ground station.
• In addition to outages or blockages due to weather, a laser communications link also has to be safe and may have times when transmissions are not allowed.
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Optical Communications Network Operations Center (NOC)
• In order to provide all of this flexibility for users, the relay network operations center must assume the responsibility for the user data flows.
• The NOC must now keep an accounting of the user data in transit within the provider system (onboard the relay or within a ground station).
• Any handovers or outages that require retransmissions or rerouting within the provider network must all be managed by the NOC transparently to the users.
• The NOC must also be able to provide the necessary insight to resolve any lost data issues reported by users.
• The LCRD Mission Operations Center (MOC) acts as a future NOC in the demonstration
Essential Experiments and Demonstrations
• Experiments will begin immediately following launch and Payload checkout
• During the first six months, the highest priority experiments will demonstrate technology readiness for the next generation TDRS infusion target– Laser Communications Link and Atmospheric Characterization– Earth-Based Relay (Next Generation TDRS)
• The remaining mission time will continue the essential experiments to collect additional data and also include:– Development of operations efficiency (handover strategies, more autonomous
ops, etc.)– Planetary/Near-Earth Relay scenarios (additional delays, reduced data rates,
non-continuous trunkline visibility)– Low Earth Orbit (LEO) - real or simulated
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SCaN’s Optical Communications Strategy for Near Earth
• SCaN has made a considerable investment in the 10 cm optical module design being used on both the Lunar Laser Communications Demonstration (LLCD) and the Laser Communications Relay Demonstration (LCRD)– In the optical module there are minor differences between the two– The major difference is in the modem (DPSK at 1.244 Gbps for LCRD and PPM
at 622 Mbps for LLCD)
• SCaN would like to re-use that design as much as possible:– Future Low Earth Orbit (LEO) compatible terminal– Future lunar missions (far side exploration)– Next Generation TDRS (perhaps with an upgraded higher rate modem)
• For missions deeper in the solar system, SCaN has made a limited investment in the Deep Space Optical Terminal (DOT) concept being worked on at JPL
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The LCRD optical communications terminal leverages previous work done for NASA
With a demonstration life of at least two years, LCRD will provide the necessary operational experience to guide NASA in developing an architecture and concept of operations for a worldwide network
• Unlike other architectures, it will demonstrate optical to optical data relay LCRD will provide an on orbit platform to test new international standards
for future interoperability• LCRD includes technology development and demonstrations beyond the optical
physical link NASA is looking forward to flying the LCRD Flight Payload as a hosted
payload on a commercial communications satellite NASA can go from this demonstration to providing an operational optical
communications service on the Next Generation Tracking and Data Relay Satellites
Summary
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