European Spaceflight
Places · Spaceport
Guiana Space Centre
Five degrees off the equator, which is as much free rotational velocity as any operating spaceport gets, and open ocean to the east. Ariane 6 and Vega fly from here.
The sky from here
This is a zone 3 sky — rural transition on the nine-grade scale, Bortle 3–4, reaching roughly magnitude 6.2–7.0 unaided. The Milky Way is clearly there but loses its detail near the horizon. Light domes are obvious in several directions.
That grade puts 106 of the catalogue within easy reach of 10×50 binoculars and 106 within a 130mm — 38 of them need no instrument at all. Genuinely dark sky — zone 2 or darker — starts about 15 km north-east.
There is no season here in which the sky fails to get properly dark — the Sun clears eighteen degrees below the horizon on all 365 nights.
At its highest the galactic centre stands 56° up, which is the difference between a Milky Way with depth in it and a smear along the horizon. Of the 110 Messier objects, none are circumpolar and every one of them rises at some point in the year.
Of everything in the catalogue, Cetus A, Virgo A and De Mairan's Nebula are the best served here, climbing to within a few degrees of straight up — an object at the zenith is being seen through the least air it will ever be seen through, and the difference against the same object low in the south is not subtle.
Read at 5.24°N 52.77°W. Darkness is estimated rather than measured; everything else follows from the latitude and holds along the whole parallel. How accurate this is.
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Questions
What part of the sky never rises at Guiana Space Centre?
Almost none of it. 5.2°N is close enough to the equator that both celestial poles sit near the horizon, and everything except the last 5.2° around the south celestial pole — under 1% of the sphere — comes up at some hour of some night. Very few places on Earth have access to as much of the sky as this one.
How many hours of true darkness does Guiana Space Centre get?
Between 9 hours 2 minutes and 9 hours 42 minutes, and it is the narrowness of that range rather than either end of it that characterises the place. This close to the equator the Sun sets steeply and at much the same hour all year, so the observing night in January is within about 40 minutes of the observing night in July. That counts only proper astronomical night, with the Sun eighteen degrees down; the merely-dark hours either side of it are longer. There is no season here, and no bad half of the year to plan around.
What orbits can be reached from Guiana Space Centre?
Anything inclined at 5.2° or more, for free. A rocket launched due east from 5.2°N arrives in an orbit inclined at 5.2° — the shallowest the site can reach without spending propellant to turn the plane — and steeper orbits are simply a matter of launching on a different heading. Steeper targets cost nothing extra: the 51.6° of the Space Station, and the near-polar sun-synchronous orbits the Earth-observation fleet uses, are all reachable directly. What the latitude charges for is the other direction: a geostationary orbit sits at 0° inclination, and all 5.2° of the difference has to be bought back with propellant that could have been payload.
How far is Guiana Space Centre from the other sites on this map?
The nearest is Alcântara Launch Center, about 1,260 km to the south-east. That is also the nearest other spaceport, with the next one 3,910 km beyond it. Measured as the great circle between coordinates, which is the shortest path across the surface and rarely the one you could travel.