moonLaser

Target array

Guide view

North up, celestial east to the left — the view through an eyepiece.

Offset from disk centre —

Apparent diameter —

Illumination —

Position angle of axis —

Schematic disk with a real terminator and true libration, no surface imagery. Selenographic east (Mare Crisium, Lunokhod 2) falls toward celestial west, so the arrays sit where you would actually see them.

Range channel

Range rate—

Light-time rate—

Gate drift per minute—

Two-way Doppler at 532 nm—

Up-leg light time—

Down-leg light time—

Transverse velocity—

Velocity aberration—

Return pattern offset here—

Diurnal aberration applied—

Array and sky conditions

Incidence on array face—

Sun elevation at the array—

Array thermal state—

Relative link index—

Libration, longitude / latitude—

Topocentric right ascension / declination—

Hour angle—

Air mass—

Refraction correction—

Sun elevation at the station—

Moon to Sun separation—

Ground station

Preset

Latitude °N Longitude °E Altitude m

Pressure hPa Temperature °C

Time

now

Hold the epoch and scrub ±12 hours to walk a target up through the sky, or watch libration swing the array around the disk.

Elevation, ±12 hours

Shaded bands are daylight and twilight at the station.

Elevation Horizon Now

The beam path

Not to scale. What the pulse actually does on its way out and back — spreading to a footprint kilometres wide, catching an array the size of a tabletop, and returning as a diffraction lobe far larger than the telescope that has to catch it.

Telescope aperture, metres Outgoing divergence, arcseconds

Footprint on the lunar surface —

Array area, out of that footprint —

Fraction of the outgoing pulse intercepted —

Return lobe diameter back here —

Fraction of the return collected —

Kept after the lobe is offset —

Photons leaving, per pulse —

Photons detected, per pulse —

Pulses needed for one detection —

In the orbital view

Your station, with its zenith line Selected array The other four arrays Laser path, with the pulse in flight

Earth and Moon sit at their true separation of about 60 Earth radii; the Moon is drawn six times oversized so it reads at that distance. Its orientation is the real one, so the arrays rotate with libration.

Lunar Ranging