ORIGINAL EDITORIAL / PRIMARY SOURCES
Research notes.
Plain-language explanations of the measurements, models, and communication systems used elsewhere in the archive.
ORBITAL TRACKING · 7 MIN
What is directly below the ISS?
How coordinates, a ground track, and reverse geocoding turn a moving point in orbit into a place on Earth.
READ NOTE ↗ EXOPLANETS · 6 MINWhat “habitable zone” actually means
Why the label is a useful first filter—not evidence of oceans, an atmosphere, or life.
READ NOTE ↗ LUNAR ORBIT · 5 MINWhy the Moon’s distance changes
Perigee, apogee, orbital shape, and why the number shown on the Moon page moves every day.
READ NOTE ↗ MISSION OPERATIONS · 8 MINHow spacecraft call home
Radio links, giant antennas, weak signals, light-time delay, and the Deep Space Network.
READ NOTE ↗