At sunset on Wednesday, the Deep Space Climate Observatory (DSCOVR) lifted off from Cape Canaveral and started its long trip toward the sun. It will give us never-before-seen views of Earth.
Liftoff of the SpaceX Falcon 9 v1.1 medium-lift rocket carrying DSCOVR. Photo: SpaceX.
In June, DSCOVR will come to rest 1% of the way from Earth to the sun at a spot called Sun-Earth L-1. At Sun-Earth L-1, the gravity fields balance with the centrifugal effects of orbit, and the satellite can “hover” on the line between us and our star.
Being on that line will give DSCOVR a special view. It will be in the only stable orbit that sees the sunlit face of the planet all day, every day. The closest comparison to what it will see is from geostationary weather satellites, like Roscosmos’s Elektro-L 1:
The Indian Ocean on October 11th, 2013, as Cyclone Phailin approached land. Image: Roscosmos.
DSCOVR will record the same motion of the weather as Elektro-L 1 does, but its imagery will be different in three ways. First, it will be in true color, showing Earth’s hues as an astronaut would see them – although no human has ever been that far away. Second, it will have fewer data gaps. (Notice how the Elektro-L 1 imagery “skips” around midday.) And, most importantly, instead of showing a view fixed over a point on the equator, DSCOVR will watch the Earth rotate from the point of view of the sun. Every image will be of noon, wherever noon is at that moment.
The main goal of DSCOVR’s Earth observation is to improve climate models. By continuously measuring how the atmosphere, land, and water of the planet absorb and reflect sunlight, scientists will learn more about long-term patterns and trends. The science is vital, but I’m more interested in the images themselves. If we think of the famous Blue Marble photograph from Apollo 17 in 1972 as a portrait, DSCOVR will be a webcam: a picture of our homeworld updating in near-realtime, in constant motion through days and seasons.
DSCOVR carries another set of instruments pointed in the other direction. Those instruments will watch the sun and the charged particles that it radiates into space – the solar wind. The clearest effect of the solar wind on Earth is the aurora, or northern and southern lights:
Aurora australis between Australia and Antarctica on July 15th, 2014. NASA photo ISS040-E-66075, by an astronaut on ISS Mission 40. Foreground: the space station’s solar panels, edge-on.
The solar wind is usually harmless, but occasional solar storms can make it strong enough to interfere with electronics on and around Earth. For example, in early 1989, an enormous solar flare was followed by a coronal mass ejection that caused a nine-hour blackout in Quebec. In late 2003, a series of geomagnetic storms damaged several satellites and jammed radio communications – including part of the GPS system – which forced airlines to reroute flights at great cost. As we rely more on space-based systems, we’re more at risk of space weather disrupting everyday life.
Workers unpack DSCOVR near Cape Canaveral a few days ago. It was built about 15 years ago and had to be carefully checked after so long in storage. This side of the spacecraft will face the sun. The instrument near the top with the round red cover is a Faraday cup, which will record protons in the solar wind once per second. Photo: NASA.
This is why the National Oceanic and Atmospheric Administration (NOAA), NASA, the Air Force, and several international partners are keen to have a new instrument sitting between us and the sun. Up to an hour before a solar storm’s effects hit Earth, DSCOVR will have measured them precisely, and forecasters at the Space Weather Prediction Center can send detailed alerts to operators of satellites and power grids, as well as the public. Following the weather metaphor, DSCOVR’s team calls it a tsunami buoy in space.
Earth (showing Australia and Antarctica) behind the second-stage engine of the Falcon 9 rocket carrying DSCOVR. Photo: SpaceX.
DSCOVR is a symbol of a lot that’s going right with space. It shows a coalition of agencies, and the private launch company SpaceX, collaborating on the kind of satellite that a global, spacefaring civilization needs. I can’t wait to see us through its sensors.