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University of Colorado Boulder — Janus Starshade Formation Flying Sensor

Last updated: 2026-04-07 (Session 82)

Summary

CU Boulder PI Webster Cash used FO to test the Janus precision alignment sensor for starshade exoplanet missions. The starshade concept — two spacecraft separated by tens of thousands of kilometers, one carrying a telescope, the other a petal-shaped occulter — requires formation flying alignment to meter-level accuracy at interplanetary distances, independent of GPS. Cash invented the shaped starshade in 2005 (Nature 2006) and the FO project validated the sensor on Masten Xombie.

Archetype: 14 (Flight-Qualified Technology Awaiting Mission) — the technology worked (TRL 4→7) but no starshade mission has been selected yet. However, starshade is now being studied for Habitable Worlds Observatory (HWO), NASA's next flagship.

FO Project

Field Value
Project 91620
Title Precision Formation Flying Sensor Testing
PI Webster Cash
Co-Is Ann F. Shipley, Anthony D. Harness, Nathan L. Parrish, Tiffany Glassman
Period 2013-12 to 2016-02
TRL 4 → 7
Status Completed
Views 843
TX TX17.2.3: Navigation Sensors
Partners CU Boulder (lead), Northrop Grumman Systems Corp (Redondo Beach, CA)

What was tested: The Janus navigation sensor on a Masten Aerospace suborbital reusable launch vehicle (sRLV). Janus provides precision alignment information independent of GPS, enabling spacecraft formation flying over large distances in deep space. The FO test gave Masten new information about vehicle behavior while validating the sensor in a flight-like environment.

Upstream Lineage

  • 2005: Cash invents shaped starshade design (Nature 2006, cited 400+ times)
  • New Worlds Observer concept: ~50m petal-shaped screen + conventional telescope, separated by tens of thousands of km, to image Earth-like planets up to 60 light years away
  • Janus sensor provides 10 billion:1 contrast by blocking host star light
  • FO project builds on lab demonstrations (SPIE 2014: "Lab demonstrations of a vision-based formation flying sensor for suborbital starshade missions")

Downstream Impact

Habitable Worlds Observatory Connection

  • HWO is the #1 recommended flagship in the 2020 Astrophysics Decadal Survey
  • Architecture decision (as of 2025): coronagraph is the baseline; starshade is NOT baselined but interface compatibility preserved. All HWO Engineering Assessment Committee architectures include external starshade compatibility but do not baseline it, citing faster-than-expected coronagraph technology progress
  • HWO Technology Maturation Project Office (TMPO) at Goddard has three technology tracks: coronagraph system, large ultrastable telescope, high-sensitivity UV/visible instrumentation. No starshade track in the formal roadmap
  • HWO25 conference (July 28-31, 2025, Johns Hopkins): inaugural open community conference, 500+ attendees, 122 talks, 177 posters. First end-to-end integrated modeling shown. No coronagraph vs. starshade reversal
  • HWO Industry Tech Maturation Contracts (Jan 5, 2026): NASA selected 7 companies — Astroscale US, BAE Systems, Busek, L3Harris, Lockheed Martin, Northrop Grumman, Zecoat — for 3-year fixed-price contracts to advance HWO technologies. Focus areas: coronagraph, large ultrastable telescope, UV/vis instrumentation. No starshade track in industry contracts. Administrator Isaacman endorsed HWO as "bold, forward-leaning science." Proposed launch ~2041.
  • Budget risk: Trump FY2027 budget proposes 47% NASA science cut. Congress restored science funding in FY2026 appropriations, but FY2027 outcome uncertain. HWO's long timeline makes it vulnerable to political cycles.
  • Cash's formation flying sensor work feeds directly into the starshade alignment problem, but with coronagraph baselined and industry contracts coronagraph-focused, the pull on this technology has further weakened since Session 54

JPL S5 Program — Closed Out (2025)

  • S5 formally concluded in 2025, having achieved all 15 milestones reviewed by ExoTAC
  • Total investment: ~$44M; achieved TRL 5 across three critical areas: starlight suppression, formation sensing and control, deployment accuracy and shape stability
  • Final milestones: dimensional stability of flight-representative truss bay (7B) and on-orbit thermal stability (8B)
  • Small-scale masks at Princeton validated contrast vs. shape model to within 25% accuracy (10⁻⁹ to 10⁻⁸ contrast)
  • Starshade Exoplanet Data Challenge remains active post-closeout
  • S5 was scoped for Roman Starshade Rendezvous and HabEx concepts; with neither funded, the program ends as a technology bank rather than a mission feed

NIAC ISEE — New Inflatable Starshade Concept (Jan 2025)

  • PI: John Mather (Nobel laureate, JWST Senior Project Scientist), NASA Goddard — not Cash
  • Phase I awarded January 2025: Inflatable Starshade for Earthlike Exoplanets (ISEE)
  • Sizes: 35m (250 kg, HWO-compatible), 60m (650 kg), 100m (1,700 kg, for pairing with ground ELTs)
  • Phase I deliverables: mass/power budgets, strength/stiffness analysis, lab tests of bonding large inflatable sheets
  • March 2026: astrobiology.com article on "shared orbiting starshade" concepts for ground-based + space telescope combinations — adjacent work

Current Status

  • Cash remains at CU Boulder CASA (Center for Astrophysics and Space Astronomy)
  • No visible public output from Cash in 2025-2026 — no new publications, grants, or HWO team membership found. May have shifted to advisory roles or reduced public activity
  • No direct contract from HWO program found in USASpending
  • The starshade community has evolved: S5 is closed, ISEE is Goddard-led (Mather, not Cash), HWO has baselined coronagraph

Assessment — Updated Session 82

The FO-validated Janus sensor remains a foundational technology for the starshade approach, but the landscape has shifted further since Session 54:

  1. S5 closed (2025): The starshade technology program is done. $44M invested, TRL 5 achieved, but no mission to feed into
  2. HWO baselined coronagraph: Starshade is preserved as an option but not funded for development. This is a meaningful downgrade from "one of two competing approaches"
  3. HWO industry contracts (Jan 2026) are coronagraph-focused: The 7 industry partners selected for 3-year tech maturation are working on coronagraph, telescope stability, and UV/vis — not starshade. This further reduces the probability of a starshade track emerging in HWO's near-term roadmap
  4. Cash is quiet: No visible public activity from the Janus PI in 2025-2026 (now 18+ months of silence)
  5. New concept work (ISEE): Inflatable starshade being studied by Mather at Goddard (NIAC Phase I, Jan 2025) — a separate lineage from Cash's work. Phase I likely wrapping up ~mid-2026
  6. Budget risk: FY2027 proposed 47% science cut could threaten HWO timeline. Congress saved FY2026, but the political environment is hostile to long-horizon flagship missions

Revised assessment: The Janus sensor is flight-qualified technology for a mission architecture that has not been selected, whose principal technology development program has closed, and whose parent mission's industry contracts are focused elsewhere. The probability of HWO deploying a starshade has continued to decrease since Session 54 — not zero, but increasingly marginal.

Timeline: FO flight test (2014-2016) → S5 closeout (2025) → HWO industry contracts bypass starshade (Jan 2026) → possible HWO decision (late 2020s) → possible mission (2040s) = 25-30 year maturation arc, with lower probability than any previous assessment.

Key People

  • Webster Cash: Professor, CU Boulder APS/CASA. Inventor of the shaped starshade concept. Research profile spans X-ray optics, starshades, and formation flying.
  • Northrop Grumman: Industry partner on FO project; also a major contractor for space telescopes (JWST prime)

Confidence

Claim Confidence Evidence
FO validated Janus sensor at TRL 7 Confirmed TechPort [91620]
Cash invented starshade concept Confirmed Nature 2006, widely cited
HWO baselined coronagraph, not starshade Confirmed HWO EAC architectures, TMPO roadmap (2025)
S5 program closed with all 15 milestones achieved Confirmed S5 Closeout Report, ExoTAC review
S5 invested ~$44M total Confirmed S5 Closeout Report
Janus sensor still relevant to starshade alignment problem Confirmed Same physics; but no funded mission to apply it to
NIAC ISEE inflatable starshade awarded to Mather (Goddard) Confirmed NASA NIAC 2025 selections
Cash has no visible 2025-2026 public output Suggestive Web search returned no recent publications or grants (checked Session 54 and 82)
No USASpending contracts found for Cash/starshade post-FO Confirmed Search returned no results
HWO industry contracts (Jan 2026) coronagraph-focused, no starshade Confirmed NASA press release Jan 5, 2026; 7 companies selected
HWO budget threatened by FY2027 proposed 47% science cut Confirmed SpaceNews, Planetary Society reporting

Cross-References

  • Psionic NDL — another FO precision navigation sensor that achieved mission infusion
  • Draper Precision Landing — similar long-arc FFRDC/non-profit technology maturation through FO