Orbital Clarity ChallengeThese technical guidelines describe what solutions are asked to measure, how well, and within what constraints. They are the technical companion to the submission form and the evaluation criteria; specifically, the “Performance” criterion scores each submission against the benchmarks defined below for each measurand and altitude regime.
The performance figures on this page are target floors, not fixed requirements. They describe the level of performance NASA believes would make a solution useful for thermospheric density specification and modeling. Applicants may propose a different target with justification — for example, a solution that trades some measurement performance for a substantial gain in cost or scalability may still be highly competitive.
Download the submission form (PDF).
Measurement objective and performance benchmarks
The core goal of this challenge is low-cost measurement of thermospheric density in low Earth orbit, at a cost and form factor that allow measurements to proliferate across commercial satellite platforms.
Thermospheric/neutral mass density is the lead measurand. Thermospheric pressure and drag acceleration are in scope as a means of determining density — including approaches that use the host spacecraft itself as a sensor of drag acceleration. Measurements of thermospheric/neutral composition (individual number density of major neutral species) are valued but not required.
Solutions should target one or both of two altitude regimes, and every applicant must identify the regime — and the altitude range within it — where their solution will meet its stated performance:
- Very low Earth orbit (VLEO): below 300 km
- Low Earth orbit (LEO): 300–800 km
The table below states the target performance for each measurand. Applicants should state their expected performance against the relevant target, with quantitative figures of merit and expected uncertainty, supported by test data, prior data, or analysis.
| Measurement type | Measurand | Altitude regime | Accuracy | Precision | Resolution |
|---|---|---|---|---|---|
| In situ | Mass density (inclusion of major-species composition preferred) | LEO or VLEO | 20% or better | 10% or better | 30 seconds or faster |
| In situ | Neutral gas pressure | LEO or VLEO | 20% or better | 5% or better | 30 seconds or faster |
| In situ | Drag acceleration | LEO or VLEO | 5% or better | 1% or better | 10 seconds or faster |
| Remote sensing1 | Major species neutral density | VLEO (90–300 km) | 10% or better | 10% or better | 5° horizontal resolution; 10 km altitude resolution |
| Remote sensing1 | Temperature profile | VLEO (90–300 km) | 10% or better | 10% or better | 5° horizontal resolution; 10 km altitude resolution |
1 Remote-sensing teams should propose to measure the neutral-atmosphere major-species density and/or the temperature profile (depending on altitude range, major species may be NO, O₂, N, or O) over as wide a range in altitude, latitude, and local time as possible, and should provide the rationale for their chosen region of operation in altitude, latitude, and local time.
Please use the NRLMSIS empirical atmosphere model as a reference for the expected thermospheric conditions — density, temperature, and composition — and how they vary with altitude, latitude, local time, and solar and geomagnetic activity across the VLEO and LEO regimes your solution would operate in.
For a broader review of thermospheric density measurement approaches and their limitations, see the review article by Bruinsma et al.
Examples of eligible solutions
Every solution in this challenge that is delivered must be compatible with integration aboard a commercial spacecraft. Within that frame, the following pathways are illustrative of the types of solutions that fit this challenge.
- Hosted in-situ sensors: instruments that directly sample the local environment from the host spacecraft — for example, measuring neutral density, composition, or pressure along the host’s orbit.
- Drag-acceleration approaches: precision measurement of drag acceleration, either through a hosted instrument or by using the host spacecraft itself as the sensor, from which thermospheric density is determined.
- Hosted remote-sensing instruments: instruments that observe the thermosphere remotely from the host spacecraft, measuring major-species density and/or temperature profiles across a range of altitudes, latitudes, and local times.
This list is not exhaustive; applicants are encouraged to propose approaches not listed here, provided they produce the target measurements and meet the requirements described on this page.
Standalone free-flying satellites, including standalone calibration satellites, are not eligible in this challenge. Every solution must fly as a hosted payload.
Solution form factor and requirements
1. Resource needs and accommodation (SWaP)
This is a low size, weight, and power (SWaP) challenge: Solutions should be designed for ready accommodation on planned and existing commercial satellites without significant modification to the host beyond mounting, thermal, and electrical interfaces.
A specific host spacecraft has not yet been selected, so no fixed mass, volume, or power envelope is published at this time. Applicants should state the assumptions they are making about the host and the range of conditions their solution could accommodate — including best estimates of mass, volume, power draw, data rate and format, pointing requirements, radiation tolerance, thermal tolerances, vibration and shock tolerances, EMI/EMC considerations, and any safety or handling limitations. Designs that remain robust across a range of host conditions will be better positioned for flight.
2. Interface specifications
Because the flight arrangement is not yet defined, firm interface control documentation is not available at this time. Applicants should design toward interfaces typical of commercial small-satellite hosted payloads and state their interface assumptions — for example, the supply voltage, data interface, and mounting approach their design expects. Interface specifications with expected attachment parameters will be published as flight arrangements mature, and teams advancing to Phase 2 will finalize their designs for hosted-payload compatibility against those specifications.
Applicants should also account for the contamination environment of a commercial host platform. Instruments with exposed detector systems, high-voltage elements, or sensitivity to volatile contamination should explain how they will tolerate that environment or what workarounds they will use — for example, covers or caps deployed on orbit after an initial outgassing period.
3. Measurement data
Applicants should describe the data their solution produces and estimate the daily data volume and peak data rate it would generate. Data downlink will be provided through the host spacecraft; solutions are not expected to carry their own communications systems.
Additional requirements
- Low-cost and producible at scale — buildable and deliverable in quantities of at least 100 units at a per-unit cost far below the current state of the art, where comparable instruments cost roughly $1M–$10M per copy (per-unit cost excludes non-recurring engineering, launch, deployment, and operations).
- Durable — designed to withstand launch loads and to operate for at least one year in the LEO or VLEO thermal and radiation environment. No total ionizing dose figure is available yet, so teams should state their own radiation assumptions.
- Debris-safe — solutions must not present a debris hazard: Any deployable elements must be retained, and approaches that intentionally release objects must describe how they meet orbital debris mitigation requirements.
- Non-interfering — designs must not interfere with the host spacecraft’s systems or other payloads. No EMI/EMC requirements are published yet, so teams should assume reasonable EMI/EMC compliance will be expected, state what they assume that entails, and explain how their design accommodates it.
Orbital parameters
NASA intends to offer each team that successfully completes Phase 3 a flight test in orbit at no cost to the team. Flight costs are covered by NASA and are excluded from applicant budgets — cost and scalability figures in a submission should reflect the solution itself, not launch or flight services.
A flight vehicle, provider, and mission have not yet been selected. Target orbits will fall within the LEO and VLEO ranges described above, but figures for inclination, mission duration, and ground contact are not currently available. Teams should make reasonable assumptions, communicate those assumptions in their submission, and demonstrate that their design remains robust if the assumptions change.