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Spacecraft

Overview

Only five spacecraft have escaped the Sun's gravity field to travel to the outer solar system toward interstellar space: Pioneer 10 and 11, Voyagers 1 and 2, and New Horizons. Any Interstellar Probe spacecraft must be autonomous, compact and lightweight, and lean on power –yet robust enough to gather data and communicate with operators on Earth. Relying on heritage, the team is using the New Horizons spacecraft as its baseline design, with incremental improvements as needed. As with the Pioneers, Voyagers and New Horizons, the baseline power source is a radioisotope thermoelectric generator, which provides reliable power over long mission lifetimes and great distances from the Sun.

For additional details on the augmented versus baseline mission payloads, please review the Example Model Payloads.

Voyagers 1 and 2 were launched in 1977 and still operate in the edges of the heliosphere.

Credit: NASA/JPL-Caltech

New Horizons has explored the Pluto system and other Kuiper Belt objects.

Credit: NASA/Johns Hopkins APL/SwRI

Augmented Payload Example Images

Click on images to enlarge and download.

This image provides a view of the full spacecraft on the particle suite side. The magnetometer boom, with two magnetometers spaced out on it, can be seen deployed here. The rigid 2.5m stacers of the PWI instrument are placed perpendicular to the spin axis, each 90° apart from each other.

This depiction shows a close up of the particle suite on a boom (from left to right): energetic particle subsystem, pick up ions, plasma subsystem, with one of the cosmic ray subsystem telescopes above the PUI instrument. The other telescope is at the base of the boom, where the two telescopes have boresights that are approximately 90° apart (+/- 45° from perpendicular to spacecraft ram), in order to observe cosmic ray anisotropies. The particle suite is on a boom in order to achieve full sky angular coverage when the spacecraft is spinning. Above the boom is the visIR spectral mapper, and to the left of the boom is the visNIR imager, which are coboresighted for the flyby. The pointing direction for the cameras, which is perpendicular to the spacecraft ram direction, is chosen for the flyby as well as the dust and extragalactic background light measurements.

Opposite the particle boom is the energetic neutral atom camera boom, with a camera that has almost full sky angular coverage when the spacecraft is spinning, with the exception of a sun-exclusion zone.

The neutral mass spectrometer, which will be measuring composition of the local interstellar medium, is seen here coboresighted with the interstellar dust analyzer. Both are accommodated to avoid field of view conflicts while pointing as close as possible to the apparent inflow direction, assuming a flyout direction of approximately 45° off the nose. This results in a pointing direction of approximately 40° off of spacecraft ram.

The bottom view of the spacecraft gives the most comprehensive picture of all the different instrument suites. It gives a full view of the plasma wave antennas and the magnetometer boom. The two different instrument booms, one for the particle suite and the other for the ENA camera, are spaced between the RTGs and the plasma wave antennas. Additionally, the neutral mass spectrometer and the interstellar dust analyzer are on the bottom of the spacecraft, while the visNIR imager and visIR spectral mapper are on the side, near the particle suite boom.

This shows another view of the ENA camera boom.

This shows another view of the particle suite boom.

This view gives a good perspective of the magnetometer boom.

This gives another view of the instrument booms, plasma wave antennas, and the magnetometer boom.

This gives a good view of the 5m high gain antenna.

This provides another view of the bottom of the spacecraft.

Example Model Payloads

Click on images to enlarge and download.

This image provides a view of the full spacecraft on the particle suite side. The magnetometer boom, with two magnetometers spaced out on it, can be seen deployed here. The 50m wire antennas of the PWI instrument are placed perpendicular to the spin axis, each 90° apart from each other.

This depiction shows a close up of the particle suite on a boom (from left to right): energetic particle subsystem, pick up ions, plasma subsystem, with one of the cosmic ray subsystem telescopes above the PUI instrument. The other telescope is at the base of the boom, where the two telescopes have boresights that are approximately 90° apart (+/- 45° from perpendicular to spacecraft ram), in order to observe cosmic ray anisotropies. The particle suite is on a boom in order to achieve full sky angular coverage when the spacecraft is spinning.

Opposite the particle boom is the energetic neutral atom camera boom, with a camera that has almost full sky angular coverage when the spacecraft is spinning, with the exception of a sun-exclusion zone. The Lyman-alpha spectrometer is next to the ENA boom, pointed in order to get a full picture of the hydrogen wall.

The neutral mass spectrometer, which will be measuring composition of the local interstellar medium, is seen here coboresighted with the interstellar dust analyzer. Both are accommodated to avoid field of view conflicts while pointing as close as possible to the apparent inflow direction, assuming a flyout direction of approximately 45° off the nose. This results in a pointing direction of approximately 40° off of the spacecraft ram.

The bottom view of the spacecraft gives the most comprehensive picture of all the different instrument suites. It gives a view of the plasma wave antennas and the magnetometer boom. The two different instrument booms, one for the particle suite and the other for the ENA camera, are spaced between the RTGs and the plasma wave antennas. Additionally, the neutral mass spectrometer and the interstellar dust analyzer are on the bottom of the spacecraft, while the Lyman-alpha spectrometer is on the side, near the ENA boom.

This shows another view of the ENA camera boom, along with the Lyman-alpha spectrometer.

This shows another view of the particle suite boom.

This view gives a good perspective of the magnetometer boom.

This gives another view of the instrument booms, plasma wave antennas, and the magnetometer boom.

This gives a good view of the true length of the 50m plasma wave antennas.

This provides another good view of the length of the plasma wave antennas.

Engineering

Concept Study Plan

The Concept Study Plan has kept the engineering team on track in terms of answering questions vital to the successful presentation of a viable potential interstellar probe. In Phase One, the required trade space was identified. Phase Two is being completed now, with the development of the baseline mission concept and potential augmentations. The final step will be to explore a potential Solar Oberth Maneuver, which will be completed during the summer of 2021.

  • Phase 1 – Identify Trade Space
    • Work with science team to develop example payloads with generic instrument types. Use existing or near existing analogues to define resource requirements such as mass, power, volume, field of view and data rates/volumes.
    • Survey previous studies and similar mission concepts to identify technology base to be considered.
    • Identify realistic mission trajectories and develop initial mission concepts
  • Phase 2 – Develop Baseline Concept and Augmentations
    • For Jupiter gravity assist cases, define a mission and spacecraft concept that accommodates the heliophysics baseline example payload.
    • Identify and conduct trades that optimize the science and spacecraft implementation
    • Develop materials information as input to heat shield design for Solar Oberth Maneuver case
    • Adapt baseline concept for planetary and astrophysics augmentations to example payload
  • Phase 3 – Solar Oberth Maneuver Concept
    • Define mission and spacecraft concept for Solar Oberth Maneuver case, if possible.

Mission Definitions

The baseline and augmented spacecraft look very similar. The only changes made re-accommodated the instruments for an augmented mission, for example ensuring that fields of view were clear for instruments. There are no changes to guidance control hardware, and the data return concept looks very similar.

Baseline Mission

  • Spinning spacecraft of about 860 kg dominated by 5m fixed antenna and 50 m PW wire antennas
  • Spacecraft architecture/block diagram typical of deep space missions
    • SpaceWire linked system with high degree of redundancy and fault tolerance
    • X-band telecommunications with fixed antenna. Selection driven by pointing requirements at end of mission to allow RF link to Earth
    • Two Next Generation RTGs for 300 We at end of mission (assumes RTG specifications consistent with Planetary Decadal Survey study assumptions)
    • Margins consistent with NASA and APL margin requirements for concept studies

Augmented Mission

  • Hybrid spinning/3-axis spacecraft virtually identical to baseline spacecraft
    • Most of the mission, spacecraft spins, change to 3-axis control for flybys. Changes to system are driven by need to provide 3-axis control and to provide instrumentation for augmented science.
  • Changes
    • Exchange PW wire antennas for 2m antennas
    • Retool payload for modified measurement requirements. Total payload resources similar to baseline case (mass, power, data return, etc)
    • No change to guidance and control instrumentation, however, software added to provide 3-axis control
    • Data return concept of operations reworked to incorporate flyby data return

Data Downlink

The table below gives the communications plan versus mission phase. The chart below gives projected total data volume per week. Together, they show that throughout the mission there are substantial amounts of data that would be transmitted back to Earth, even out to 1000 AU and beyond. There’s plenty of science to be done with the available data downlink, and study team scientists have already begin looking at how this would be divided up amongst various instruments and measurements.

Baseline / Augmented Trajectory Study

The image below is one of the trajectory studies that the Interstellar Probe Study team has completed. Cases have been examined for potential baseline and augmented missions, and they have shown that for any given launch, there is an opportunity to achieve speeds in the range of 7 to 8 Astronomical Units (AU) per year.

Fly-away Speed

  • Is a function of mass, launch vehicle, direction and launch date
  • Red areas show highest speed for a given launch year from 2031 to 2041
  • Able to achieve greater than 7 AU/year for all launch years (860 kg spacecraft mass)
  • Fly-away speed changes by 0.17 AU/year for a 50 kg mass change