New eye in the sky: DSCOVR to watch over Earth and Sun

After nearly a decade in storage the Deep Space Climate Observatory (DSCOVR) last week started its 110-day, 1.5 million-kilometre journey. It will be a watchful guardian, perfectly balanced between the Earth and Sun, where it will help take our planet’s temperature and give advance warning of damaging solar eruptions.

But the historic launch that took place at 6.03pm (EST) on 11 February from Cape Canaveral was not the double bill we anticipated. It was intended that the rocket carrying DSCOVR would also make history. After pushing DSCOVR into space, the Falcon 9 rocket – showpiece of the aerospace company SpaceX – was meant to touch down gently on to a waiting barge in the Atlantic Ocean, demonstrating CEO Elon Musk’s vision of a re-usable (and therefore cheaper) space rocket.

Third time was the charm for the Falcon 9. Two previous attempts were scrubbed – once because the Cape Canaveral radar tracker failed, and then because of gusty winds in the upper atmosphere. On the third day the  weather at the launch site was perfect – but on the Atlantic Ocean it was anything but. The barge, had it been on the ocean, would have been battered by three-storey-high waves so SpaceX aimed the returning rocket at a patch of water instead.

A safe landing was only ever a bonus; the main goal was to launch DSCOVR. (A Falcon 9 landing attempt in January got close to the barge but ran out of hydraulic fuel for its stabiliser fins. It spun out of control and crashed at the last minute in a fiery explosion.) 

But while a Falcon 9 landing attempt must wait for another day, DSCOVR is finally on its way. Development of DSCOVR began in 1998 when it was known as Triana. Former US vice president Al Gore championed the observatory for the live images of Earth it would beam back to us.

The project was cancelled in 2001 but repurposed in 2009 when NASA and National Oceanic and Atmospheric Administration wanted a satellite to replace the ageing Advanced Composition Explorer space weather monitor.

DSCOVR will take 110 days to traverse to its destination between the Earth and the Sun. Its target is Lagrange Point 1, a location where the gravity of the Earth counteracts that of the Sun. This is crucial as ordinarily the closer you are to the Sun, the stronger the gravity you experience and the faster you have to move to stay in orbit. Yet at Lagrange Point 1 the Earth's gravity allows a satellite to move more slowly than otherwise and keep pace with the Earth's orbit ensuring both planet and star stay in view. Imagine a 150-million-kilometre rope tethering both Earth and tiny DSCOVR to the Sun, and that the Sun is swinging that rope around it.

From this special vantage point DSCOVR will have a permanent view of the Sun and the sunlit side of Earth. This is valuable for measuring the Earth’s albedo – the amount of light our planet reflects from its variously darker and lighter surfaces. Measuring it is a key step in creating more accurate climate models.

Whenever the Sun erupts with a coronal mass ejection the satellite will also take the first hit and beam a prediction of the severity of the oncoming blast back to Earth. This will give us a precious few minutes to prepare for the collision during which satellites orbiting Earth can be shut down and electricity grids can decrease their power load to better handle sudden damaging power surges. As well as warning of approaching coronal mass ejections, DSCOVR will improve other space weather forecasts, such as the strength of the stream of plasma released from the Sun called the solar wind. This is important as even minor peaks in the solar wind can dramatically affect GPS or long-wave radio transmission. A good forecast also means a better chance of knowing when to catch the beautiful Northern or Southern Lights (aurora borealis and aurora australis) which are formed when particles from the solar wind interact with our atmosphere.

While DSCOVR sails on to its lonely position between the Earth and Sun, SpaceX will try landing a rocket on a barge again. Over the next three months it has five launches scheduled, sending satellites into orbit and bringing supplies to the International Space Station in the Dragon capsule, which is like a robotic delivery truck. These launches have to be timed perfectly to intersect the Space Station’s orbit. It travels at 7.6 kilometres per second so even a few seconds’ delay could result in the spacecraft missing by many kilometres.

The next scheduled launch is on 27 February so make sure to get a ringside seat.

After Falcon 9’s successful launch last week and a landing that came only 10 metres from where the barge would have been, it seems SpaceX now only needs the weather to cooperate to enter the history books.

See also: What’s behind the hole in the Sun?