NOAA-20
Weather forecasting depends less on watching clouds than on measuring the atmosphere, and most of those measurements come from polar-orbiting satellites like this one — circling pole to pole while the planet turns underneath.
What makes NOAA-20 different
The whole planet, twice a day
A polar orbit plus a rotating Earth means the entire globe passes underneath in two passes a day — once in daylight, once at night. Nothing is skipped, including the oceans and poles where nobody is taking readings from the ground.
It measures, it does not just photograph
Its instruments sound the atmosphere for temperature and humidity at many altitudes. Those vertical profiles are what numerical weather models actually consume; the pictures are a by-product.
Low enough to see detail
At about 830 km it resolves far more finely than a geostationary satellite forty times further out. The trade is that it visits twice a day rather than watching continuously.
Part of a relay, not alone
NOAA-20 flies with Suomi NPP and NOAA-21 on the same track, spaced so that observations arrive more often than any single satellite could manage.
NOAA-20 launched in November 2017 as the first of the JPSS series and is one of the workhorses behind the forecast you check in the morning. Its sun-synchronous orbit crosses the equator at the same local time on every pass, giving consistent lighting and a stable measurement geometry. The distinction from GOES-16 is worth holding onto: geostationary satellites watch one hemisphere constantly but from far away, while polar orbiters see everywhere at high resolution but only in snapshots. Modern forecasting is the two combined, and models deprived of polar sounding data degrade sharply within days.
Frequently asked questions
What is a polar-orbiting satellite?
One that passes near both poles on each orbit. Because Earth rotates beneath it, successive orbits cover different longitudes and the whole planet is observed within about a day.
How is this different from GOES-16?
GOES-16 hangs over one hemisphere continuously from 35,800 km. NOAA-20 flies at 830 km and covers everywhere twice a day at much higher resolution. Forecasting uses both.
Does NOAA-20 predict the weather?
It measures. Its temperature and humidity profiles feed numerical models, and the models produce the forecast.
Can I see NOAA-20?
Occasionally, as a faint moving point on a dark clear night. It is far dimmer than the ISS.