Landing & Radio

Shaded squares are ground coloured by how much of the likely landing area a receiver standing there would probably hear: each landing point counted by its chance of being heard, from the distance, the terrain in the way (radio bends over a ridge and arrives weaker, not not at all: a diffraction loss by ITU-R P.526 as P.1812 applies it to a terrain path, rather than a simple line of sight), and the few dB a real signal wanders from its prediction with where exactly the antennas are, what is round them and which way a landed rocket’s antenna happens to lie. That is why walking further is not always better, and why a landing at the edge of range counts as a coin toss rather than a yes. The search starts 5.0 km around you at 50 m and, if nothing there hears enough, works outwards a kilometre at a time to 8 km, coarsening as it goes: the ground that works can easily be two or three kilometres away, which is the thing you cannot pick off a flat map. The plain runs 16.8 km across at 0 m sampling, so there is room to drag the pins about; nothing recomputes until you ask it to. With the weather looked up, the wind, gusts and temperature at the ground and the winds above, to about 31 km, all come from the NOAA GFS model held on this server, for any day from 113 days back to 11 ahead, interpolated to the launch time and placed at their heights above the pad's own ground; the model's temperatures give the air's thinning with height, and a canopy falls faster where the air is thinner. How far the landings spread comes from the NOAA GEFS ensemble held here too (31 runs of the same model from slightly different starts, for Europe, North America and Australia and New Zealand, from 49 days back to 9 ahead): each simulated flight flies one run's winds around the GFS ones, so the zone widens on a day the forecast is unsure and when the launch is days ahead, with a fixed allowance on top for what a 50 km model cannot know about the field, and gusts and lulls through the flight sized from the forecast gusts; on a sunny day the thermals as well, each flight dropped into one rising or sinking draught sized from the model’s boundary layer depth and the surface heating worked out from its sunshine, cloud and temperature. Elsewhere, or where no ensemble is held for the time, the fixed allowance alone sets the spread. With the weather entered by hand the winds are the ones you give, or stretched upwards from the ground reading, and the air is the standard atmosphere from the pad's height.