Places · Spaceport
Alcântara Launch Center
Two degrees from the equator on the Atlantic coast — geographically one of the best launch sites there is, and still waiting for a vehicle to use it properly.
The sky from here
Measured at these coordinates the sky is zone 5: suburban, which is Bortle 5–6 and a naked-eye limit of about magnitude 5.2–6.0. The Milky Way is invisible or nearly so. Clouds are lit from below. You can read a newspaper outside on a clear night.
Of the 110 Messier objects, 15 are an unaided-eye target from a sky this dark, 82 are comfortable in 10×50s and 85 in a 130mm reflector. You would have to get roughly 30 km north before the sky reaches Bortle 2.
Every night of the year reaches full astronomical darkness at this latitude; the Sun always gets its eighteen degrees below the horizon, which places much further from the equator cannot say.
At its highest the galactic centre stands 63° 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.
Cetus A, De Mairan's Nebula and Orion Nebula pass close to the zenith from this latitude — 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 2.37°S 44.40°W. Darkness is estimated rather than measured; everything else follows from the latitude and holds along the whole parallel. How accurate this is.
Nearby
Questions
What part of the sky never rises at Alcântara Launch Center?
Barely any of it, which is the rare thing about this latitude. From 2.4°S the hidden cap is only 2.4° across — under 1% of the celestial sphere, tucked around the north celestial pole — and everything else crosses the horizon at some point in the year. Both hemispheres of sky are available from here, which is true of almost nowhere with a telescope on it.
How many hours of true darkness does Alcântara Launch Center get?
Between 9 hours 14 minutes and 9 hours 37 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 24 minutes of the observing night in July. Astronomical darkness is the Sun more than eighteen degrees below the horizon, which is a stricter thing than the Sun being down. There is no season here, and no bad half of the year to plan around.
What orbits can be reached from Alcântara Launch Center?
Anything inclined at 2.4° or more, for free. A rocket launched due east from 2.4°S arrives in an orbit inclined at 2.4° — 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. The Space Station's 51.6°, and any polar or sun-synchronous orbit, are all available from here. Shallower is where it gets expensive. Every one of the 2.4° between here and the 0° of a geostationary belt is paid for in a plane change, which is why equatorial pads are worth building even in inconvenient places.
How far is Alcântara Launch Center from the other sites on this map?
Its closest neighbour on this map is Guiana Space Centre, 1,260 km away to the north-west. That is also the nearest other spaceport, with the next one 5,160 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.