Spaceports and orbits (Capstone 2 week)

Track 2 culminates here. With orbital mechanics (Week 7), SGP4 propagation (Week 8), and ground-station visibility (Week 9) in hand, you can answer the central matching question of operational space-domain awareness: given an orbital regime, which spaceports can serve it? And given a spaceport, which orbits can be efficiently reached?

The geometric constraint

The fundamental constraint is simple: a rocket launched due east (the most efficient azimuth, gaining maximum benefit from Earth's rotation) ends up in an orbit with inclination equal to the launch site's latitude. To reach higher inclinations, you launch progressively more northward or southward, sacrificing the eastward velocity bonus.

Some rules of thumb that fall out of the math:

• Minimum achievable inclination from a launch site is the site's latitude. Kourou (5.2°N) can reach equatorial orbits efficiently; Plesetsk (62.9°N) cannot reach any orbit with inclination below 62.9° without a costly plane change.
• Sun-synchronous orbits (i ≈ 98°) require launches to the south. Vandenberg (34.7°N) is ideal because trajectories head south over the open Pacific. Cape Canaveral (28.5°N) cannot do SSO safely because southward trajectories would overfly populated Florida and the Caribbean.
• GEO insertions favor equatorial sites. A GEO target requires zero inclination; reaching it from Kourou costs ~250 m/s less delta-V than from Cape Canaveral (28°). Over a 15-year satellite life, that's roughly 200 kg of saved fuel — substantial.
• Molniya orbits (i = 63.4°) match high-latitude launch sites. Russia's Plesetsk and Vostochny are at exactly the right latitude to insert directly.

Spaceport-to-orbit table

A reference matrix for the world's active spaceports:

Coverage polygons

For Earth-observation satellites, the more practical question is the swath: the strip of Earth's surface within the sensor's field of view at any moment. For a sensor with swath width w, the coverage polygon is the ground track buffered by w/2. For Landsat 9 (185 km swath), buffer the ground track by 92.5 km on each side. For a hypothetical 1000-km-swath sensor (e.g. SAR), buffer by 500 km.

Coverage is asymmetric in time: the ascending pass and descending pass cover different ground, and a single satellite revisits the same swath only every ~16 days for Landsat or ~5 days for Sentinel-2 (which has two satellites).

The capstone

The Week 10 lab is the start of Capstone 2: Ground-Track Coverage Tool — a Python tool that, given any TLE, outputs the 24-hour ground track as GeoJSON, a 1000-km-swath coverage polygon, and a country-overflight table with dwell time per country. The full rubric is on the capstone page; finishing it earns the Certified Orbital Analyst credential. Track 3 (Remote Sensing Specialist) starts next week, where the focus shifts from where the satellite is to what it sees.