LAGEOS-1 and LAGEOS-2, two satellites tracked by laser

Whose measurements these are

The International Laser Ranging Service turns laser echoes into a published orbit, every week.

Each week the service’s analysis centres take the laser ranges from the station network and each fits an orbit through them with its own software, and a combination centre brings those orbits together into one. The combined orbit behind this page is made at ASI, with a backup made at JCET, and the files were fetched from the EUROLAS Data Center at DGFI-TUM.

Who made them: The International Laser Ranging Service: its stations, its analysis centres and its combination centres
The centres: Analysis centres ASI, BKG, CNES, DGFI, ESA, GFZ, JCET and NSGF. Combination centres ILRSA, made at ASI, and ILRSB, made at JCET.
The product: ILRS combined orbits of LAGEOS-1 and LAGEOS-2, doi.org/10.5067/SLR/SLR_ILRSORB_001. The weeks used run from 23 August to 19 September 2026, fetched from the EUROLAS Data Center at DGFI-TUM, edc.dgfi.tum.de.
The citation the service asks for: Pearlman, M.R., Noll, C.E., Pavlis, E.C. et al., “The ILRS: approaching 20 years and planning for the future”, J Geod 93, 2161–2180 (2019), doi.org/10.1007/s00190-019-01241-1. The service also asks that SLR, satellite laser ranging, be given as a keyword.

What happened

Two mirror-covered spheres circle the Earth and are tracked by laser.

Stations on the ground fire pulses of light at them and time the echo. From those echoes, an orbit is published every week.

Laser ranging, drawn and not to scale. A station on the ground times a pulse of light to a sphere and back. Each sphere is covered in small reflectors that send the light home.

LAGEOS-1 was designed by NASA and launched in 1976, the first spacecraft made for nothing but high-precision laser ranging. LAGEOS-2 follows the same design, was built by the Italian Space Agency and went up in 1992. Each carries 426 reflectors.

Why send up something that does nothing? A plain, heavy sphere is as simple a thing as can be put in orbit, so where it goes says a great deal about what is pulling on it. LAGEOS-1 goes round every 225 minutes, nearly six thousand kilometres up.

The published orbit is good to a few centimetres. It is a fit to the laser ranges by the analysis centres and not a raw measurement, and it is the yardstick the model was held to.

What the model did

Told where each satellite was at one moment, the model said where it would be a week later. It was off by 32 metres on one and 22 on the other.

The model is given a published position and velocity at a single instant, and after that it is left alone. A week is more than forty trips round the Earth and some three million kilometres of travel.

The passing grade was fixed before any model was scored, at one orbit, one day and one week ahead. Forty-two runs were made across the two satellites, and every mark was met. LAGEOS-2 flies a different orbit, and the model was run on it unchanged.

Two other Super Intelligences then repeated the comparison, each with its own code for the turning of the Earth, and landed on the same distances to within centimetres.

Met

LAGEOS-1, off by32 metres

LAGEOS-2, off by22 metres

The worst distance after seven days. The two bars are to scale with each other.

Where it stops

Twenty-eight days, two orbits, a week ahead at most. Asked for another date, another orbit or a longer forecast, it stops and says why.

What it was tested for

LAGEOS-1 and LAGEOS-2 in free flight, from a published position and velocity, for at most seven days.
Twenty-eight calendar days, 23 August to 19 September 2026.
Weeks held back from its design, of which one LAGEOS-1 week and all four LAGEOS-2 weeks were fully blind.

Past that, and what its own description says of itself

Another date, another orbit or a longer forecast: the model stops and names the reason.
It has no drag, no light reflected from the Earth and no ocean tide, and its Sun and Moon are approximate.
Its structure was chosen after a ladder of structures fixed in advance had failed on two opened weeks. The tide, sunlight pressure and relativity were added afterwards, and the held-back weeks are what make it a test.
The starting state has to be turned into the model’s own frame first. Fed in as published, fixed to the Earth’s crust, it is about 20 metres off within one orbit.
The yardstick is itself a fit to laser ranges and not a raw measurement.

For the reader who wants every number

In the verifier’s own words.

Everything above is this page’s telling. What follows is the verifier’s own, exact and whole: four parts of the description of the model aerospace/satellite_lageos1, as read on the morning of 11 October 2026. Where the verifier says card it means a model, where it says line it means a pass mark, and where it says refuses it means the model stops there and says why.

The real thingobject

The laser-ranging satellite LAGEOS-1 in free flight, started from its published position and velocity at one instant. The same card, unchanged, was also run on the satellite LAGEOS-2.

The passing grade, fixed firstpass_line

Fixed before any model was scored: within 1 m of the published orbit after one revolution, 10 m after one day and 100 m after seven days.

The resultresult

Every line met on 42 runs, none refused. LAGEOS-1: worst distance 0.65 m after one revolution, 3.8 m after one day, 32 m after seven days. LAGEOS-2: 0.34 m, 2.9 m and 22 m.

Its limitslimits

The card's structure was chosen after a ladder of structures fixed in advance failed on two opened weeks; the tide, sunlight pressure and relativity were added afterwards. The held-back weeks are what make it a test: one LAGEOS-1 week and all four LAGEOS-2 weeks were fully blind; the other LAGEOS-1 week had been downloaded earlier and its analysis centres compared with each other, with no model involved. The published orbit is itself a fit by analysis centres to laser ranges, good to a few centimetres; it is not a raw measurement. The start state is turned into the card's frame outside the engine; a crust-fixed state fed in directly is about 20 m off within one revolution. Free flight only; compared on 28 calendar days, 2026-08-23 to 2026-09-19, for at most seven days from a published state, on the two orbits of LAGEOS-1 and LAGEOS-2 and nowhere between or beside them; the card refuses other dates, other orbits and longer forecasts by name. No drag, no light reflected from the Earth, no ocean tide; the Sun and the Moon are approximate. Run once and checked twice. Repeated independently on 2026-10-07 by Grok, another developer's model, with its own comparison and its own Earth-orientation code: the same six worst distances to the millimetre. Scored a third time from the protocol alone on 2026-10-10 by an agent that did not write the card, with its own Earth-orientation code: worst distances within 7.8 cm of the record.

Hand this one to your agent.

https://mcp.zerotrustphysics.com/mcp

Open to any agent.

Something to paste

Connect to https://mcp.zerotrustphysics.com/mcp and read the model aerospace/satellite_lageos1. Then tell me what it is, and why it might matter to me.

Give it this page too.

What it will find

This model’s own description: what it takes in, where it stops, the orbits it was held to and how it did, in its own words.

If these are your measurements.

The model’s account of these two orbits is there for any agent to read, in its own words. It could be held to something only because the ranging stations, the analysis centres and the combination centres publish their work every week. John Kruze would be glad to hear what it got wrong about the real satellites.

Give the address and this page to your own agent first. Then write or call.

Write: [email protected]
Call: 928-264-7883