A physics engine, and a verification tool enforced on top of it. PhysWall inverts a closed, published, non-linear physical law at a single measurement point — and refuses when the inverse is not unique. Seven laws, one engine, and the same refusal in all of them.
A number NASA already publishes, every minute, that is one step from a distance.
JPL calls the measurement ranging: the DSN times a signal out and back, and the round-trip light time (RTLT, twice the one-way OWLT) fixes the distance with no model of the orbit at all.
The Deep Space Network posts which antenna is talking to which spacecraft, at what data rate, and how long a signal takes to get there and back. Divide that by two, multiply by the speed of light, and you have a range — measured, not modelled.
distance = RTLT × c / 2
RTLT 0.00 s → 400 km just after separation
2.00 s → 300,000 km
2.56 s → 384,400 km the Moon
10.01 s → 1,500,000 km L2
12.34 s → 1,850,000 km
The feed carries light time to hundredths of a second, which is 1,499 km of range — about a tenth of a percent at L2. Quoting a distance to the kilometre from it would be inventing four digits.
which orbit plane no needs a direction, not a range how long one loop takes no needs position over a full revolution on the reference? no needs the reference and a position
A distance inside its declared band tells you the spacecraft is where it should be along one axis. The other two are not in the number, and the honest verdict on them is no verdict — with the missing input named, so somebody can go and get it.
Seven published constraints for one L2 mission, each carrying its source. A bound with no citation cannot fail a measurement, so the tool refuses to grade against one.
Most of them come from a 2017 design paper written for a spacecraft that weighed 7,728 kg. The one that flew weighs about 10,500. If a measurement lands outside the box, the first explanation is that the box is out of date.
Not thermal, which is the usual guess. The mission's own flight dynamics team wrote in 2024 that the requirement which most constrains the design is the ability to downlink at least 1.3 terabytes of science data a day through one ground station, and that this restricts the mission to unusually small-amplitude orbits compared with JWST.
⚠ Which makes the data rate — also on the live feed, next to the light time — the most interesting number there.
PhysWall was developed and architected by Gadi Zion.
Built on PhysWall — the same engine reads antenna bandwidth, conductor loss, bit erasure and heat limits. It answers what the measurement implies, and refuses when the measurement cannot say.⚠ Check this instead of believing it. Every number here reproduces from a source that is named, and the claims that turned out wrong are still printed next to what replaced them. The same engine runs all of these — it asks how much a measurement allows you to conclude, and refuses the same way in every field. The same engine runs all of these — it asks how much a measurement allows you to conclude, and refuses the same way in every field. How to check each one →