August 31st, 2021 by Joseph M. Smith, NASA EOSDIS Science Writer
“Not bad for a shoebox.”
This quip, uttered by an engineer at NASA’s Wallops Island Near Earth Network (NEN) receiving station on March 22, 2019, is something NASA oceanographer Gene Carl Feldman will never forget.
The comment came in response to the successful downlink and processing of the first image from the HawkEye imager aboard the University of North Carolina-Wilmington’s SeaHawk CubeSat, currently in low-Earth orbit approximately 575 kilometers above the surface.
The goal of the SeaHawk mission was to prove a concept: that it is possible to collect scientifically credible ocean color data comparable to that of previous ocean color satellite missions from a 3U (or unit) CubeSat, a small, cube-shaped satellite (also known as a nanosatellite) measuring just 10-centimeters x 10-centimeters x 30-centimeters. The first successful download of an image from HawkEye proved it was.
“The mission could have ended at that moment, and we could have declared 100 percent success,” said Feldman, who specializes in ocean color remote sensing. “This was the first X-band downlink from a CubeSat that NASA had ever done. The data came down, it was processed flawlessly through the system — it was amazing! Everything worked. Here you have this 11-meter dish collecting data from something you can hold in one hand.”
The mission could have ended at that time, but, of course, it didn’t. Although pursued as a proof-of-concept, Feldman admits he had bigger plans for SeaHawk from the start.
“I didn’t think it would be worth NASA’s investment to do a one-off, get one image, prove the concept, and go home,” he said. “My goal from the beginning was to integrate this mission into the infrastructure that we have built over the past 25 years to support ocean color satellites, and to demonstrate that a CubeSat can be treated like a normal, credible scientific mission.”
Bigger isn’t necessarily better—at least where satellites are concerned. Modern “CubeSat” satellites are smaller and more numerous than ever.
The CubeSat takes its name from its dimensions; it is made up of multiples of 10×10×11 centimeter cubic units. A basic CubeSat weighs roughly 3 pounds (1.3 kilograms) and looks a good deal like a portable speaker.
Early satellites started out small, too. Launched in 1957, Sputnik weighed around 184 pounds (83 kilograms). America’s first satellite, Explorer I, weighed just under 31 lbs (14 kg). Then, as the desire for more sensors grew, so did the size of satellites. The first American weather satellite, TIROS I, was a hefty 270 lbs (122 kg). But recent years have seen a reversal of this trend.
Like modern cell phones, satellites have benefited from more compact and more powerful computing technology. (A 1980s cell phone was an expensive, brick-sized gadget that could only place phone calls and store a couple dozen numbers.) Satellites, too, have sprouted new cameras and sensors. Take the IPEX CubeSat developed by NASA’s Jet Propulsion Laboratory (45 seconds into the video below); it can track features like forest fires, volcanic eruptions, and algae blooms.
THE UPSIDES OF BEING SMALL
A satellite today can be a “hitchhiker,” aboard a larger mission, as the video below mentions. Or, a CubeSat can be launched from the International Space Station.
Because they are smaller, CubeSats tend to cost less, so research organizations can deploy more of them. That means more spatial coverage for monitoring the Earth. Where researchers once relied on two or three larger satellites to keep an eye on weather over the Pacific Ocean, now, handfuls of smaller satellites can help with the job.