In the days leading up to a launch at Vandenberg Space Force Base, most of the attention is focused on preparing the rocket and payload for their trip to space. In this case, that’s NOAA’s Joint Polar Satellite System-2 (JPSS-2) satellite, and its secondary payload, LOFTID.
But there’s another operation happening at the base that makes these launches possible. About 1.5 miles north of the Visitor’s Center is the Weather Operations Center, or “The Weather Shop,” where a 15-member team monitors the weather around the clock. And in a meeting of worlds, satellites from the JPSS series provide an important source of the data that feeds their weather forecast.
Vandenberg is located in the seaside city of Lompoc, California, an area known for the so-called marine layer that comes in overnight, blanketing the area with low clouds and fog.
While the marine layer affects visibility, it’s not a threat to launch safety. More hazardous to a launch are winds, rain and lightning, said Launch Weather Officer Capt. Zackery Zounes. In fact, he said, if the right conditions exist inside a cloud, a rocket itself can trigger lightning. Lightning is especially hazardous, because it can short circuit electronics and navigation systems.
The onsite meteorologists watch wind closely too. And Vandenberg is a windy place.
“You don't want the rocket to get pushed by the wind and tip over,” Zounes said. “You don't want it to be pushed off its trajectory.”
Fortunately, the 99,000-acre base has a robust network of instruments to help monitor weather conditions. On base are 26 wind towers with more than 200 instruments.
“Small changes in wind direction and wind speed have a huge impact on the space lift mission here. So we have to be very good at what we do,” said Launch Weather Officer Captain Addison Nichols. “Thankfully, Vanderberg is one of the few places that has a robust weather instrumentation network that allows us to do our job.”
Weather surveillance aircraft that fly through the area on launch day provide measurements of cloud heights, temperature and other important data to assess the risk of lightning.
But the planes don’t fly higher than 30,000 feet. In order to track a developing thunderstorm, you need to know the conditions at a slightly higher altitude of 40,000 or 50,000 feet. And since rockets travel through the upper atmosphere, it’s important to understand what’s happening much higher than that.
Enter weather balloons.
At Vandenberg’s Surface and Upper Air Observatory, Senior Weather Observers like Daniel Day launch weather balloons with instruments attached to the bottom called radiosondes. The radiosondes measure wind speed and direction, temperature, pressure and humidity high into the atmosphere. The balloons expand as they rise into the atmosphere until at their biggest, they’re about the size of a greyhound bus. They typically fly between 100,000 to 120,000 feet.
Weather safety officers track the data being fed from the balloons as they rise, and feed them into a model.
Weather models are fed by data from weather balloons, radar, ground-based instruments and weather satellites like JPSS-2. In fact, 85% of the data feeding today's weather forecast models come from polar-orbiting satellites like those in the JPSS fleet.
Adding more polar-orbiting weather satellites, like JPSS-2, could improve the accuracy of models by increasing the frequency and amount of data collected over the upstream oceans, Zounes said.
All this data will be stitched together to provide a reliable weather forecast for the JPSS-2 satellite’s launch day.
“Out here, it is rocket science,” Nichols said, “and so we have to be very, very precise.”