# Presentation: 575965

## Intersatellite Communications:Considerations for Distributed Observing Systems and Mission Operations

**4****th**** International Symposium: Reducing the Cost of Spacecraft Ground Systems and Operations**
**7****th**** Annual Workshop: Reducing the Cost of Space Operations**
**Johns Hopkins University, Applied Physics Laboratory**
**April 24–27, 2001**
**Stephen J. Talabac**
**Commerce One**

## 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## ...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*

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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*. ESE’s technology investment strategy over the next 5 to 10 years focuses on the instrument, spacecraft, and information technologies needed to make this future possible.”

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## Earth Science Enterprise Strategic PlanNear-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.

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## Earth Science Enterprise Strategic PlanMid-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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- April 24-27, 2001

## Earth Science Enterprise Strategic PlanLong-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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- April 24-27, 2001

## 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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- April 24-27, 2001

## Space Science Enterprise Strategic PlanNear-term (2000-2005)

- Study the dynamics of the Sun’s atmosphere and interior, research the interactions between the solar wind and Earth’s magnetosphere, and view solar coronal mass ejections in 3-D
- Obtain images of the Earth’s 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*.

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## Space Science Enterprise Strategic PlanMid-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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- April 24-27, 2001

## Space Science Enterprise Strategic PlanLong-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

**Science Processing Center**** **

**Science Processing Center**** **

- Graphic Credit: NASA/GSFC *2000 Survey of Distributed Spacecraft Technologies and Architectures for NASA’s Earth Science Enterprise in the 2010-2025 Timeframe*

- Bent pipe communications

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## Space Mission Architecture – A Future Sensor Web

- Graphic Credit: *NASA/GSFC: 2000 Survey of Distributed Spacecraft Technologies and Architectures for NASA’s Earth Science Enterprise in the 2010-2025 Timeframe*

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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*

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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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- April 24-27, 2001

## Distributed Observing Platform Concepts

- Constellation-X: the search for black holes

- ST5: Nanosat Constellation Trailblazer

- STEREO: stereo views of the Sun

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- April 24-27, 2001

## 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!*

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## A Distributed Spacecraft Mission Vocabulary1There 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)

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## A Distributed Spacecraft Mission Vocabulary...and 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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... don’t 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.

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## “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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## Constellation ExampleTeledesic

- 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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- April 24-27, 2001

## Constellation ExampleGlobal 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## ConstellationsHomogeneous 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## “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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## “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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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.

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## An “Accretionary Formation”The 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## “Formation Flyer” Large Effective Aperture ObservatoryConstellation-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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## “Formation Flyer”Laser 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## Mission Architecture NomenclatureMotherships 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 H&S 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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

**Sun-Earth Line**

**L2**

**1.5 million km**

**L1**

**1.5 million km**

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## Interspacecraft Communications TopologiesConstellations

**Adjacent planes**

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## Interspacecraft Communications TopologiesClusters

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## Interspacecraft Communications TopologiesString 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 there’s 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## Information that Needs to be Exchanged

- Spacecraft and Instrument H&S 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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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- April 24-27, 2001

## 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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.

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

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## Interspacecraft Comms: Potential Uses/BenefitsFor 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 a*ggregate* 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 H&S engineering telemetry
- Routine, emergency out-of-limits
- Receive science instrument data
- Potential bandwidth problem if high rate, high volume

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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 H&S 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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?

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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.

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001

## 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 TT&C and mission operations systems (e.g., “expert” or “rule-based” systems)

- Reducing the Cost of Space Operations Intersatellite Communications Workshop

- April 24-27, 2001