Spaceports and orbits (Capstone 2 week)
Track 2 culminates here: combine ground station coverage analysis with orbital mechanics to answer the matching question — given an orbit, which spaceport? Given a spaceport, which orbits? The capstone delivers a ground-track coverage tool.
Mahia Peninsula in Aotearoa New Zealand and Wallops in Virginia both host Rocket Lab Electron launches. Why these two sites?
The answer is in the geometry — which orbits each site can efficiently reach. This week brings together orbital mechanics and spaceport geography into one practical question: given an orbit you want, which pad?
Learning objectives
- Match spaceport latitude to feasible orbital inclinations
- Explain why Kourou is the GEO launch capital
- Identify which spaceports can serve sun-synchronous orbits
- Build a coverage polygon for a hypothetical 1000-km swath sensor
Primer
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:
| Spaceport | Latitude | Best for |
|---|---|---|
| Kourou | 5.2°N | GEO, equatorial |
| Sriharikota | 13.7°N | GEO, mid-inclination |
| Wenchang | 19.6°N | GEO, lunar (Long March 5) |
| Cape Canaveral / Kennedy | 28.5°N | LEO, GTO, ISS (with dogleg) |
| Vandenberg | 34.7°N | Polar, SSO |
| Wallops | 37.9°N | Mid-inclination LEO |
| Tanegashima | 30.4°N | GEO, SSO |
| Baikonur | 46.0°N | ISS (51.6°), Soyuz LEO |
| Plesetsk | 62.9°N | Molniya, polar |
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.
Connecting to Hawaiʻi: Pacific Voyaging Society and Mahia
Mahia Peninsula in Aotearoa New Zealand is home to Rocket Lab's Launch Complex 1 — the only private orbital spaceport in the Southern Hemisphere. Mahia is at 39°S, which gives Electron access to a wide range of inclinations including sun-synchronous polar orbits popular for Earth observation. Pacific voyagers have known Mahia's coordinates for centuries (it's an important navigation landmark on the journey between Aotearoa and Rarotonga). The Pacific Voyaging Society has cultural ties throughout the region, and Hōkūleʻa has visited Aotearoa. The Pacific is one ocean; the launch network sits inside it.
Hands-on lab: Ground-Track Coverage Tool (capstone start)
Given any TLE, output: (1) 24h ground track as GeoJSON, (2) 1000-km-swath coverage polygon, (3) country-overflight table with dwell time per country. This is the deliverable for Capstone 2.
Quiz — click an answer to check it
No grade, no shame. Tap any option; you'll see if it's right plus the answer if not. The point is to notice what you already know and what's still settling.
- It's coldest
- Equatorial latitude maximizes velocity bonus from Earth's rotation
- It's the cheapest
- It has the best weather
- GEO
- Equatorial orbits
- Polar orbits
- Inclinations of 51.6° and higher
- Equatorial
- Highly inclined polar (~98°)
- GEO
- Molniya
- Cold air
- Trajectories head south over open Pacific
- Cheap fuel
- Closer to Hawaiʻi
- The launch site's latitude
- 180 minus latitude
- Always 90
- Depends on rocket only
Reflection
Take five minutes with this. Write your answer somewhere. Carry it into next week.