@NorthLightAlert How long of a delay between DSCOVR and Earth?
— Spencer Sills (@OntPhotog) August 30, 2016
Great Question, Thanks Spencer,
The Deep Space Climate Observatory, or DSCOVR, is a satellite launched in 2015 carrying several instruments for measuring space weather. It is stationed about 1.5 millions kilometers from Earth at the gravitational balance point between Earth and the Sun known as Lagrange One. The data from this satellite is available on the space weather prediction center’s website, and it is also used to power the NLN DSCOVR Real Time Solar Wind graphics on this site.
Being 1.5 million kilometers away means there is a lag time between when solar events hit DSCOVR and when they arrive at Earth. Clouds of charged particles that travel on the solar wind, such as CMEs and solar storms, typically travel at between 350 and 800 km/s. At those speeds, it takes between 30 and 75 minutes for events measured at DSCOVR to arrive at Earth. When the solar wind is moving faster, like during a coronal hole high speed wind stream or while Coronal Mass Ejection solar storm is passing, the lag time is less. When wind speeds are more ambient, the lag time is longer. Here’s a helpful chart to help see the relationship between wind speed and lag between DSCOVR and Earth:
There is currently no way of measuring the orientation of the magnetic fields of clouds traveling on the solar wind until they reach DSCOVR. Space weather forecasters are dependent on the measurements taken at the satellite to seed the models that predict aurora. This is why accurate KP predictions can only be made 30-75 minutes in advance. In addition to letting aurora hunters on Earth know what to expect, the data also provides lead time to near earth satellite operators to know if they need to put their satellites in hibernation or protective modes to shield from magnetic fields that could damage sensitive electronics on board.
Fun Fact – DSCOVR also hosts the EPIC (Earth Polychromatic Imaging Camera) instrument, famously championed by Al Gore. This camera beams a true-color image of Earth about once every two hours. You can see the images it is sending back by following the EPIC twitter account. Read about all the specs of the camera on board here.