Glitch delays launch of hurricane-watching microsatellites

It will be at least another day until NASA can get its set of eight microsatellites into Earth’s orbit to observe how tropical storms form, helping scientists better predict the intensity of life- and property-threatening hurricanes.

The space agency scrubbed Monday’s satellite drop-off midflight after engineers realized that the hydraulic pump on the plane carrying the Pegasus XL rocket, with the satellites on board, failed to release the latches that would have freed Pegasus to take off for low-Earth orbit, where it would have dropped the satellites.

“The aircraft is on its way back with the Pegasus XL rocket still safely attached,” NASA reported online Monday morning after canceling the mission. “The next possible launch opportunity is Tuesday, pending resolution of the pump issue,” said the agency.

If the pump is fixed and the mission resumes Tuesday, the piloted L-1011 Stargazer aircraft will take off from Cape Canaveral Air Force Station again in the morning, with Pegasus XL attached to its underbelly. Both aircraft and rocket were built by Dulles, Va.-based aerospace and defense company Orbital ATK. When the Stargazer reaches about 40,000 feet over the Atlantic Ocean – a few thousand feet higher than commercial airlines reach – it will release Pegasus.

Then Pegasus will free-fall for five seconds before igniting its first-stage rocket motor to help launch itself to low-Earth orbit, a strip of near-Earth space that stretches between 100 miles and 1,200 miles above sea level. Once there, Pegasus will deliver the constellation of eight microsatellite observatories, known collectively as the Cyclone Global Navigation Satellite System, or CYGNSS, in about 10 minutes, according to Orbital ATK’s web site. The eight instruments, built by the Southwest Research Institute in San Antonio, Tex. will orbit the tropics, where most cyclones and hurricanes form.

“For the most part, we can predict track very easily,” says Derek Posselt, a University of Michigan professor who is a deputy principal investigator for CYGNSS, in a video. “We still have a very hard time knowing how intense the storms will be when they get where they’re going. The intensity of hurricanes is really what causes all the damage.”

CYGNSS will use radio signals from four GPS satellites, the same ones that beam directions to the mapping apps on our phones, to measure the wind speed near the oceans. As Space.com explains:

The Earth's surface acts like a mirror, and reflects the GPS signals back into space. If there is no wind, the signal is relatively clear, just like the light from a reflected moon is clear on calm water, Ruf said. When the wind picks up, the "image" formed by the radio signals is blurry because the radio waves scatter, in the same way that a reflected moon on the water is broken up by wavelets.

Using eight satellites helps scientists increase the area of Earth that can be measured, according to NASA. The satellites will be deployed separately around the planet, with successive satellites passing over the same region every 12 minutes. As the CYGNSS and GPS satellites move around the earth, their collaboration will could more quickly provide information about wind speed over the entire tropics: every few hours compared to every few days for a single satellite.

"This sampling strategy will overcome the limitations of a previous single, wide-swath approach," said Chris Ruf, a University of Michigan scientist and the mission's principal investigator, in a statement online.