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Intersatellite Communications: Considerations for Distributed Observing Systems and Mission Operatio

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Title: Intersatellite Communications: Considerations for Distributed Observing Systems and Mission Operatio


1
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

2
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

3
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

4
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

5
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.

6
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.

7
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.

8
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.

9
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.

10
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.

11
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.

12
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

13
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
14
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

15
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

16
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

17
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.

18
Distributed Observing Platform Concepts
STEREO stereo views of the Sun
Constellation-X the search for black holes
ST5 Nanosat Constellation Trailblazer
19
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!

20
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)
21
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

22
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.

23
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

24
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.

25
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
26
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

27
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

28
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

29
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.

30
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

31
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
32
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

33
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

34
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

35
LEO Aggregations
Constellation
String of Pearls
Cluster
36
Elliptical Orbit Aggregations
Constellation
String of Pearls
Cluster
37
Lissajous Orbits
L2
1.5 million km
1.5 million km
Sun-Earth Line
L1
38
Interspacecraft Communications TopologiesConstell
ations
Adjacent planes
39
Interspacecraft Communications TopologiesClusters
40
Interspacecraft Communications TopologiesString
of Pearls
41
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

42
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

43
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

44
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

45
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

46
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.

47
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

48
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

49
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

50
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

51
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

52
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?

54
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)
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