Intersatellite Communications: Considerations for Distributed Observing Systems and Mission Operatio

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Intersatellite CommunicationsConsiderations for
Distributed Observing Systems and Mission
Operations

• 4th International Symposium Reducing the Cost of
  Spacecraft Ground Systems and Operations
• 7th Annual Workshop Reducing the Cost of Space
  Operations
• Johns Hopkins University, Applied Physics
  Laboratory
• April 2427, 2001
• Stephen J. Talabac
• Commerce One

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Agenda

• The Drivers for Interspacecraft Communications
• Space Mission Architectures Present and Future
• Distributed Observing Systems Overview and
  Mission Taxonomy
• Interspacecraft Communications Architectures and
  Topologies
• Information that can be Exchanged
• Potential Uses and Benefits
• Potential Impacts to Mission Operations
• Some Thoughts and Candidate Recommendations

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What are the Drivers for Interspacecraft
Communications?

• NASA Near- mid- and long-term strategic plans
  (2000-2025 timeframe)
• HQ, Earth Science Enterprise, Space Science
  Enterprise
• Innovative Science Observing Concepts
• Formation Flying Missions
• Collaborative Earth- and Space-Science
  Observations
• Autonomous Event Recognition, Reconfiguration,
  and Response
• Sensor Webs
• Evolving Technologies
• MEMS microelectronics
• Electron beam lithography systems will contribute
  to the development of nanospacecraft components
  with extremely small mass
• The challenge nanospacecraft transmitter/receiver
  mass vs. on-board communications infrastructure
  and power for effective RF or optical link
  closure
• RF, optical, and digital communications
  technologies
• Communications protocols standards
• Mature terrestrial protocols Network (IP, IPv6),
  Transport (UDP, TCP), Application (FTP)
• NASA space communications protocols CCSDS suite,
  CCSDS Proximity-1, SCPS

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and a key necessity Reduce Mission Ops Costs!

• A critical impact of distributed spacecraft
  missions
• NASA cannot afford a linear increase in the
  number of spacecraft to translate into a linear
  increase in mission operations personnel ground
  system costs!
• Ultimate goal? - Ground system mission
  operations staff for a single S/C mission is the
  same as future distributed S/C mission

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NASA Strategic Plan

• Long-term plans 2012 - 2025
• Long-term benefits of the ESE program will
  include 10-day weather and pollution forecasts,
  5-day volcanic eruption advance warnings, 15- to
  20-month El Niño forecasts, and 10-year
  predictions of the regional impact of climate
  change. To obtain the observations needed for
  this level of prediction, NASA envisions an
  intelligent network of multiple observation types
  and vantage points using new technologies such as
  tiny, inexpensive microsatellites and
  nanosatellites. These systems will be
  reconfigurable and autonomous, with overlapping
  measurements for calibration and validation.
  ESEs technology investment strategy over the
  next 5 to 10 years focuses on the instrument,
  spacecraft, and information technologies needed
  to make this future possible.

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Earth Science Enterprise Strategic PlanNear-term
(2000-2005)

• NASA is pursuing architecture improvements that
  include
• intelligent platform and sensor control
• better space/ground communications
• linking multiple data sets to view the Earth as a
  system
• increasing the number of data providers and data
  users in Government and the private sector.
• Implement satellite formation flying to improve
  science return
• New Millennium Program to validate revolutionary
  technologies in space.

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Earth Science Enterprise Strategic PlanMid-term
(2006-2011)

• Conduct research to achieve 7- to 10-day weather
  forecasts.
• Quantify the global fresh water cycle, variation
  in terrestrial and marine ecosystems, and forest
  and ocean carbon stocks.
• Assimilate ocean surface winds, tropospheric
  winds, and precipitation into climate and weather
  forecasting models.
• Employ distributed computing and data mining
  techniques for Earth system modeling
• Implement autonomous satellite control and
  advanced instruments
• Demonstrate a new generation of small instruments.

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Earth Science Enterprise Strategic PlanLong-term
(2012-2025)

• Conduct research to achieve 10- to 14-day weather
  and pollution forecasts, 10-year climate
  forecasts, 15- to 20-month El Niño forecasts, and
  12-month rain rate.
• Assess sea-level rise and effects and predict
  regional impacts of decadal climate change.
• Deploy cooperative satellite constellations,
  advanced instruments, and intelligent sensor webs
• Migrate selected observations from geosynchronous
  and Low-Earth Orbits to libration points (L1 and
  L2).
• Design instruments for new scientific challenges
  deploy and develop a collaborative synthetic
  environment to facilitate understanding and
  enable remote use of models and results.
• Collaborate in an international global observing
  and information system improve operational
  systems with new technology.

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Space Science Enterprise Strategic Plan

• Many future mission concepts require
  constellations of platforms that act as a single
  mission spacecraft for coordinated observations
  or in situ measurements, or act as a single
  virtual instrument (e.g., interferometry or
  distributed optical systems). Major areas for
  work in distributed spacecraft control are
  advanced autonomous guidance, navigation, and
  control architectures formation initialization
  and maintenance fault detection and recovery
  and intersatellite communications.
• Very advanced space systems will be
  self-reliant, self-commanding, and even
  inquisitive. These intelligent space systems must
  be able to plan and conduct measurements based
  on current or historical observations or inputs
  recognize phenomena of interest and concentrate
  activities accordingly and monitor and maintain
  desired status or configuration over long periods
  of time without frequent communication with
  ground.

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Space Science Enterprise Strategic PlanNear-term
(2000-2005)

• Study the dynamics of the Suns atmosphere and
  interior, research the interactions between the
  solar wind and Earths magnetosphere, and view
  solar coronal mass ejections in 3-D
• Obtain images of the Earths magnetosphere during
  geomagnetic storms, search for evidence of water
  on Mars, and characterize the number and orbits
  of Near Earth Objects.
• Test two independent spacecraft flying as an
  optical interferometer, and demonstrate flying
  three subminiature spacecraft as a single system.

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Space Science Enterprise Strategic PlanMid-term
(2006-2011)

• Understand the detailed physics of our
  magnetosphere, study physics of the outer Solar
  atmosphere by flying through it, analyze detailed
  structure of the magnetosphere using a
  constellation with many microsatellites.
• Expand understanding of space weather using
  solar, radiation belt, and ionospheric mappers.
• Infuse revolutionary technologies into
  operational missions. Includes autonomous
  robotics and sample return gossamer apertures
  for imaging and spectroscopy by great
  observatories, constellations of cooperating
  nanosatellites, bioinformatics, and advanced
  propulsion and optical communication systems for
  ultra-deep space probes.

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Space Science Enterprise Strategic PlanLong-term
(2012-2025)

• Develop an integrated understanding of space
  weather by deploying a network of spacecraft
  throughout the Earth-Sun system.
• Clarify the larger context for life in our solar
  system with missions to Europa, Titan, or other
  sites of potential prebiotic chemistry

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Space Mission Architecture - Today
Bent pipe communications
Science Processing Center
Science Processing Center
Graphic Credit NASA/GSFC 2000 Survey of
Distributed Spacecraft Technologies and
Architectures for NASAs Earth Science Enterprise
in the 2010-2025 Timeframe
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Space Mission Architecture - Today

• Classic stovepipe science data collection and
  mission operations
• Single or separate spacecraft missions with
  little or no dynamic planning for opportunistic
  science observations
• No real time collaborative information sharing
  between sensors, spacecraft, or investigators
• Bent pipe interspacecraft communications
• via TDRSS in support of command uplinks,
  telemetry downlinks

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Space Mission Architecture A Future Sensor Web

• Graphic Credit NASA/GSFC 2000 Survey of
  Distributed Spacecraft Technologies and
  Architectures for NASAs Earth Science Enterprise
  in the 2010-2025 Timeframe

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Space Mission Architecture - Tomorrow

• High degree of synergy between a diverse suite of
  platforms
• Space-based
• Atmospheric (e.g., aircraft, balloons)
• Land (e.g., river gauges)
• Sea (e.g., buoys)
• Automated science data collection and mission
  operations
• On-board spectral signature detection algorithms
• Multiple spacecraft and platforms perform dynamic
  planning for targets of opportunity
• Real time collaborative information sharing
  between sensors, spacecraft, or investigators
• Interspacecraft communications becomes an
  intrinsic characteristic of space platforms

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The Future Space Mission Paradigm

• The long held paradigm of deploying and operating
  single spacecraft missions will be changed by the
  deployment and operation of Distributed Observing
  Systems.
• Constellations
• Formation Flyers
• Sensor Webs
• Interspacecraft communications can offer benefits
  to mission operations, however it will also
  impose other challenges that must be identified,
  understood, and resolved.
• The increase in the numbers of spacecraft to be
  monitored and controlled cannot result in a
  corresponding linear increase in mission
  operations costs.

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Distributed Observing Platform Concepts
STEREO stereo views of the Sun
Constellation-X the search for black holes
ST5 Nanosat Constellation Trailblazer
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A Distributed Observing System Vocabulary

• What is the terminology being used today?
• What implications do these terms have relative to
  our perceptions and assumptions about what
  interspacecraft communications mechanisms are
  needed and why they are needed?
• and the vocabulary, and the list of adjectives,
  appears to be growing rapidly!

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A Distributed Spacecraft Mission
Vocabulary1There are a lot of terms out there !

• Spacecraft Aggregations
• spacecraft constellations
• homogeneous constellations
• heterogeneous constellations
• reconfigurable constellations
• string of pearls constellation
• spacecraft confederations
• clusters
• loose clusters
• swarms

• Formation Flying Vocabulary
• formation flyers
• accretionary formations
• active formations
• tight formations
• loose formations
• precision formation flying
• tandem flyers
• cooperative maneuvering
• mother ships
• drones

Note (1) List compiled and organized by Stephen
Talabac (Commerce One) and Tony Barrett (NASA/JPL)
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A Distributed Spacecraft Mission Vocabularyand
there are even more terms!

• Mission Vocabulary
• coincident mapping
• collaborative missions
• collaborative sensor webs
• cooperative missions
• distributed spacecraft
• multispacecraft missions
• multimission platforms
• scout sensors
• sensor webs
• virtual instruments
• virtual missions
• virtual platforms
• virtual webs

• Autonomy Vocabulary
• autonomy
• intelligent distributed spacecraft
• remote agent
• semi-autonomy

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Some Candidate Definitions

• Note The following examples are not necessarily
  widely accepted or adopted definitions. Hopefully
  they will serve to show how these terms are being
  used, and what potential implications they may
  have on the considerations for interspacecraft
  communications and mission operations.
• Therefore... dont assume that your definition
  and assumed intrinsic mission characteristics are
  necessarily the same as what the other person may
  have in mind for the same vocabulary word.

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Constellation

• A space mission that has been formulated to
  consist of two or more spacecraft and placed on
  orbit for the purpose of making observations to
  achieve a common science objective and where one
  spacecraft alone is insufficient to meet this
  objective.
• Multispectral observing
• Same phenomena, multiple observation points
• Very large effective aperture observatories
• Magnetospheric mapping (i.e., multispatial,
  concurrent observations)
• Leonardo mission - multiple, reconfigurable
  laboratories on-orbit
• Stereo or long baseline interferometer
  observations
• Geometric (e.g., tetrahedral formation for
  electromagnetic fields)
• Often implies implementation of particular Earth
  orbit (i.e., Walker)
• Often employed by the low earth orbiting (LEO)
  global communications and geolocation missions
  (e.g., Orbcomm, Teledesic, GPS).
• Typical interspacecraft communications topology
  in-plane and adjacent plane

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Constellation ExampleTeledesic

• Boeing, Motorola and LM for launch services
• Private investors Bill Gates, Saudi Prince
  Alwaleed Bin Talal
• Global, broadband Internet-in-the-Sky
  w/fiber-like QoS
• 288 low-Earth-orbit Ka-band satellites
• 12 planes 24 spacecraft per plane at 1,375 km
  altitude
• Inter-satellite communication links with S/C in
  the same and adjacent orbital planes.
• Non-hierarchical mesh, or "geodesic," network
  tolerant of faults and local congestion
• Planned service beginning 2003
• D/L at 64 Mbps U/L at 2 Mbps.

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Constellation ExampleGlobal Star

• International consortium of telecom providers
• Voice, data, fax, messaging and other telecom
  services
• Orbital characteristics
• 48 spacecraft 8 planes, 6 S/C per plane 4 spare
  S/C
• 1,414 km, 520 inclination - coverage 700N to 700S
  latitude
• Communication between user and S/C via gateway
• No S/C-to-S/C communications

Graphic Globalstar
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ConstellationsHomogeneous or Heterogeneous?

• Homogeneous Constellation
• Constellations whose member spacecraft employ
  identical bus, payload, and operational
  characteristics.
• The spacecraft are, in essence, clones of one
  another and may be mass produced.
• Not meant to imply that they are all placed
  on-orbit all at the same time.
• Heterogeneous Constellation
• Constellations whose member spacecraft employ
  different bus, payload, and perhaps operational
  characteristics.
• Implications for interspacecraft communications
• Communications protocol standards to promote
  heterogeneous spacecraft network interoperability

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Reconfigurable Constellation

• A distributed spacecraft observing system that
  possesses the ability to change one or more
  intrinsic characteristics while on orbit.
• Example Leonardo ESE laboratory in space
• Some of these characteristics may include any or
  all of the following
• Orbit
• Attitude
• Relative spacing
• Coordination of observations with other
  spacecraft
• Cluster size
• Virtual laboratory instrument suite to be used
  for conducting an observation
• Implications for interspacecraft communications
• Adaptable/reconfigurable/multiple communications
  protocols
• RF range to achieve link closure, line-of-sight,
  orbital relationships
• Pointing control, knowledge of whereabouts of
  other spacecraft

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Formation Flyer

• Two or more spacecraft that conduct a science
  mission such that the relative distances and 3D
  spatial relationships (i.e., distances, angular
  relationships, relative velocities between all
  spacecraft) are preserved for the respective
  orbits of all spacecraft that comprise the
  formation.
• Formation flyer configurations may be desired or
  required to meet certain science objectives.
• Interferometry
• Large Effective Apertures
• Measure Electromagnetic Field Vectors
• Implications for interspacecraft communications
• Pointing vs. omnidirectional signal propagation
• Multicast or broadcast protocols
• Reliable data transfer protocol critical for
  formation control
• Half vs. full duplex links to meet mission
  operations scenarios

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Additional Formation Flyer terms

• Tight and Loose Formations
• Subjective descriptions of the degree precision
  and accuracy needed to be maintained between the
  spacecraft that comprise the formation
• Precision Formation Flying
• A subjective term referring to the required
  preciseness required of a particular formation
• There do not appear to be any particular set of
  objective metrology standards as what exactly
  constitutes precise
• Tandem Flyers
• Two or more spacecraft that follow one another in
  the same orbital plane.
• Accretionary Formation
• A distributed spacecraft mission whose individual
  S/C members are added to the mission over time.

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An Accretionary FormationThe EOS AM-Train

• A formation that comes into being or evolves
  into a constellation as additional spacecraft are
  placed on orbit
• No preconceived plan to create constellation from
  the outset
• The EOS AM Train Landsat-7, EO-1, Terra, SAC-C
• The EOS PM Train Aqua, Aura, Cloudsat,
  Picasso-CENA

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Formation Flyer Large Effective Aperture
ObservatoryConstellation-X

• Next Generation X-ray Observatory
• 4 identical spacecraft
• Two coaligned telescope systems per spacecraft
• Yields large effective X-ray collecting area
• 3 year mission design 5 years desired
• Orbit outer Lagrangian point L2
• Avoids earth thermal interference and X-ray
  source occultations

Graphic NASA/GSFC
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Formation FlyerLaser Interferometer Space
Antenna (LISA)

• Mission
• Observe gravitational waves from galactic and
  extra-galactic binary systems
• 3 S/C flying 5 million km apart in the shape of
  an equilateral triangle.
• Lasers in each spacecraft will be used to measure
  changes in the 5 million km optical path lengths
  with a precision of 20 picometers.
• Core technologies
• Inertial Sensors
• Micronewton Thrusters
• Laser Interferometry
• Planned launch 2008

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Mission Architecture NomenclatureMotherships and
Drones

• Mothership
• Presupposes a specific constellation architecture
  where a particular spacecraft serves as the
  central focal point for the constellation
  communication, and/or as general coordinator of
  all constellation activities.
• It may or may not initiate commands or act on
  drone telemetry data (engineering HS or
  instrument payload data)
• It may serve as
• a way station for store-and-forward or
  bent-pipe communications to/from Earth
• a centralized computational engine and large
  capacity mass store for the mission
• Drone
• Presupposes a specific constellation architecture
  where particular spacecraft serve as the arms
  and legs of a constellation
• Makes and reports observations and status to the
  mothership
• Accepts and acts on mothership commands
• Mothership routes telemetry data to Earth and
  accepts commands from Earth

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A Taxonomy of Constellation Orbits

• Constellation orbits
• Will be a key driver relative to how
  interspacecraft communications may be conducted.
• Orbits and S/C configurations within orbits will
  impact the ground segment and mission operations
  support.
• Based upon JPL study
• Multiple Mission Platform Taxonomy A. Barrett
  JPL/CIT, Jan. 30, 2001

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LEO Aggregations
Constellation
String of Pearls
Cluster
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Elliptical Orbit Aggregations
Constellation
String of Pearls
Cluster
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Lissajous Orbits
L2
1.5 million km
1.5 million km
Sun-Earth Line
L1
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Interspacecraft Communications TopologiesConstell
ations
Adjacent planes
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Interspacecraft Communications TopologiesClusters
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Interspacecraft Communications TopologiesString
of Pearls
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Architectural Implications for Interspacecraft
Communications

• Constellations
• Knowledge of the whereabouts of member
  spacecraft within their orbits is reasonably well
  constrained.
• Spacecraft immediately ahead of or behind
  another in the same orbital plane
• Phasing relationships between spacecraft in
  adjacent planes
• Homogeneous Constellations
• Communications infrastructure is inherently the
  same
• Simplifies communications architecture since
  theres only one solution set implemented for the
  protocol stack (e.g., ISO/OSI 7 layer model
  components)
• Heterogeneous Constellations
• Drives need for standard communications protocol
  stacks
• Facilitate interoperability between S/C and
  ground segment
• Reduce mission implementation and ops costs
• Mitigate implementation risk

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Architectural Implications for Interspacecraft
Communications

• Formation Fliers
• Knowledge of relationship between S/C that
  comprise the formation may simplify
  communications architecture
• Point-to-point
• Broadcast
• Proximity
• May permit low power communications especially
  important for low mass nanospacecraft
• Accretionary Formations
• Since they are not a priori known to come into
  being, standards are a must for communications
  protocol layers 1-4, 7 if these S/C might
  eventually communicate among one another

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Information that Needs to be Exchanged

• Spacecraft and Instrument HS Telemetry Data
• Characterized by relatively low data rates, low
  volumes
• Spacecraft operational status messages
• S/C orbit and attitude information
• Instrument(s) mode(s) of operation
• Instrument Pointing information
• Spacecraft Instrument Data
• Can be characterized by relatively high volumes
  and high data rates
• Typically unidirectional
• Collaborative missions may require bi-directional
  science data exchange
• May be used to facilitate distributed space-based
  computing
• On-board spectral (signal) signature processing
• Event recognition software
• Event response software
• Duty cycle will depend upon mission needs

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Information that May be Exchanged

• Ancillary information
• Most likely characterized by low rate, low volume
• Interspacecraft range and range-rate
• Status messages that facilitate or help to
  coordinate science observations, on-board
  processing status, etc.
• Science instrument calibration coefficients/tables
  
• Rate of data exchange and duty cycle of link
  utilization will depend upon individual mission
  needs

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Mission Needs Ops Concepts will Drive Protocol
Issues

• Differences between space terrestrial
  communications environments
• Spatial relationship between two communicating
  S/C is continually changing
• In and out of RF range
• In and out of line-of-sight
• Changing pointing angles
• Available (on-board) communications transmitter
  power to close the link
• Directional (RF,Optical) less transmit power
  pointing knowledge required
• Omnidirectional more transmit power required
  broadcast can create duplicate packets in network
• Handling lost packets
• Terrestrial networks assume congestion slow down
  packet traffic to compensate
• Space networks assume noisy link re-transmit
  packet as soon as practicable
• Propagation delays can be (but are not
  necessarily) longer

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Mission Needs Ops Concepts will Drive Protocol
Issues

• IP, UDP/TCP, FTP
• Mature, robust, open layered protocol
  architecture
• In wide commercial use for terrestrial
  applications
• Promotes interoperability between space and
  terrestrial networks
• Widespread use promotes lower ground system
  implementation costs
• Mitigates implementation risk and shortens
  implementation schedule
• Familiarity (terminology, concepts, usage) with
  user community
• Out-of-the box implementation of TCP slow-start
  algorithm may not be suitable to every space
  mission
• CCSDS
• Mature and in wide use for NASA space missions
• Interoperability with other foreign space- and
  ground- networks
• Well adapted to noisy space communications
  environment
• SCPS and Proximity-1 emerging to address current
  protocol deficiencies vis-a-vis terrestrial
  protocols use in future constellation
  communications.

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Interspacecraft Comms Potential
Uses/BenefitsFor S/C presently not within view
of a ground station

• Route all uplinks to the S/C that is within view
  of ground station
• Ground station antenna and support equipment
• S/C contact activity planning scheduling
  independent of ground station
• GEO-like nearly-continuous contacts may be
  possible with any S/C
• An increase of the uplink data rate may be
  required to serve multiple S/C
• Multiple S/C yield aggregate downlink data rates
  that may necessitate wider bandwidth (i.e.,
  higher data rate) to the ground
• Uplink route commands to one, some, all
  spacecraft
• Routine, emergency
• Receive HS engineering telemetry
• Routine, emergency out-of-limits
• Receive science instrument data
• Potential bandwidth problem if high rate, high
  volume

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Interspacecraft Comms Potential Uses/Benefits
For S/C presently within view of a ground station

• Formation flying or cluster missions
• Contact with just one S/C in the cluster may
  eliminate multiple, successive uplink contacts
  for each S/C in cluster
• Uplink one set of commands to mothership which
  serves as a router-in-space for all drone
  spacecraft

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Interspacecraft Comms Potential Uses/Benefits

• Independent of ground station view
• Unplanned science events, opportunistic science
• Automated identification (e.g., autonomous
  spectral/signal detection)
• Autonomous mission reconfiguration
• Notify or cue other spacecraft to conduct
  coordinated observations
• Event notification to mission operations
• Especially when S/C is not in view of ground
  station for long times (e.g., highly elliptical
  orbits)
• Anomaly identification and resolution

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Mission Operations Present and Future

• The present
• Mission operation are simple (e.g., SMEX, survey
  missions) to challenging (e.g., HST, AM-train)
  depending upon mission design and ops concept
• The future
• Challenging even for relatively simple (e.g.,
  survey) mission designs
• Multiple S/C for each mission
• More complex mission observation planning
  scenarios
• Potentially increased time to plan ground station
  contacts and create command loads
• Increased impact on ground station resources
  (e.g., antennas)
• Shorter duration between contacts for formation
  flyers or clusters
• Larger aggregate return link data volumes

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Potential Impacts to Mission Operations

• If interspacecraft communications requires
  pointing and if it is not performed autonomously
  on-orbit
• Plan and schedule contact times and pointing
  angles for communicating S/C
• Additional mission ops responsibility and ground
  resources to plan, schedule, and upload
  communications activity commands and data
• Times when S/C can communicate
• On-board resources required
• Pointing information
• Monitoring system performance, especially when
  things go wrong
• Additional engineering HS telemetry data
  relative to comms subsystems to monitor and
  interpret
• Transmitter/receiver status
• On-board data buffer utilization (e.g.,
  packets/files sent/received)
• Communications traffic volume, duty cycle
• Communications error rates
• Reconfigure the communications network between
  spacecraft to facilitate work-arounds,
  degradations, failures

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Potential Impacts to Mission Operations

• Data routing to the ground from a S/C not in view
  of a ground station
• Are ground equipment resources available?
• Antennas and front-end electronics
• Front-end processors
• Ground data storage
• Communications networks
• Planning science observations becomes
  intrinsically more complex and more than one
  observation scenario may be available due to
  multiple S/C.
• Need robust science observation activity
  planning, scheduling, resource utilization, and
  conflict resolution tools
• Simulators may be used to better identify and
  evaluate several alternative what if scenarios
• Rule-based assistants may evaluate and
  recommend optimal performance criteria depending
  upon mission complexity
• On-board recorder management becomes more complex

53
Potential Impacts to Mission Operations

• Commanding
• Increases in complexity if the mission permits
  commands to be routed to S/C other than those in
  view of the ground station.
• Protocols such as IP (and IPv6 with multicasting)
  could be beneficial if suited to mission
  parameters
• Telemetry monitoring
• If routed through the constellation, telemetry
  data may be available nearly continuously from
  all S/C not just during those periods when a
  pass occurs.
• Impacts ground system resource utilization and
  mission ops personnel utilization.
• Today after loss-of-signal, ground resources are
  often released, and reconfigured. Mission ops
  personnel perform other functions when no S/C
  contact is in progress.
• Tomorrow But what if spacecraft contacts were
  effectively continuous from multiple spacecraft?

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Potential Impacts to Mission Operations

• Navigation planning
• Tight formations will likely require high
  fidelity simulations to ensure collision
  avoidance and to test various what if
  navigation alternatives.

55
Conclusions and Candidate Recommendations

• Alternative mission architectures, as well as
  functional and performance objectives for
  distributed space observing systems require a
  variety of interspacecraft communications
  solutions
• Regardless of the details, mission operations
  ground resources and especially mission
  operations staff workload will be impacted
  without the luxury of increased mission
  operations budgets
• Greater on-board autonomy and more effective
  ground-based automation will be beneficial and
  contribute to alleviate the impact to mission
  operations
• Simulation software will be highly desirable by
  helping to identify alternative mission scenarios
  and to objectively and quantitatively assess
  specific impacts upon science missions in the
  design and operational phases
• Introduce advanced concepts into control centers
  and ground systems
• Goal-oriented commanding
• Mothership may serve as central relay for drones
• Automated TTC and mission operations systems
  (e.g., expert or rule-based systems)