It Takes a Lot of Big Science to Make the Best Small Satellites

You never know what turns history will take.

In 1905, in his modest flat in Bern, Albert Einstein wrote the famed paper on his theory of relativity, explaining forces like gravity and inertia and transforming the science of physics.

He also laid the foundation for incredible technologies he could not have foreseen, including GPS, computers and small, spacefaring satellites that do everything from monitor the weather to defend the nation. Raytheon is building such satellites now, proving daily the value of Einstein's work.

“We’re taking what Einstein wrote 112 years ago and applying it to meet market demands today,” explained Wallis Laughrey, vice president at Raytheon's Space and Airborne Systems business. “It’s really all about generating higher-quality imagery in a smaller, more cost-efficient package.”

Small satellites are perfect to meet the growing need for space-based imaging, used for weather science and other efforts. Launches aren’t cheap and they don’t happen every day. The smartest way to keep costs down is to control payload size and weight.

Bottom line: If you can make the payloads smaller and lighter, you can fit more satellites on a rocket at a lower price.

Honey, I shrunk the optics

Raytheon is using silicon carbide to make replicated optics (think lenses and reflectors) for telescopes and other small-satellite sensors. Aluminum, beryllium and glass are usually the go-to materials, but silicon carbide delivers equal or even greater performance at a fraction of the cost.

“Silicon carbide is one of the lightest, hardest and strongest materials on earth, making it perfect for use in space,” said senior program manager Ben Graham. “It has exceptional thermal conductivity, shock resistance and low thermal expansion, so it can stand up to the harshest of environments.”

The manufacturing process itself is fascinating. Material scientists take silicon carbide powder, suspend it in a graphite matrix, add molten silicon and heat it to very high temperatures to create silicon carbide. The end result is a strong, lightweight monolithic component that, in the intermediate stages, can be machined ten times faster than glass.

Selfies from space

You have the optics. Now you need the film, or rather, a focal plane array.

FPAs convert optical images into electrical signals that can then be read and processed.

“Einstein’s model of the photoelectric effect inspired the basis for detectors in today's digital for FPAs,” said principal engineering fellow Jeff Puschell. “What happens is, when light in the right wavelength range hits a FPA detector, an electron or other photo carrier is set free inside the detector. A capacitor captures and measures those carriers at regular intervals, and the image is captured electronically." 

FPAs are being built to capture more and more pixels, increasing the demand for data processing. To prevent payload growth, Raytheon uses reconfigurable electronics to process multiple data streams without boosting the size of the processor. 

Hold steady

If you don’t hold still while taking a photo, it’s blurry and the film is useless. In space, a steering mirror is used to correct the shaking called jitter, and to keep sensors on target.

Raytheon steering mirrors produce crisper, quality images. They’re incredibly quiet, which translates to less shaking and greater accuracy. Plus, they help sensors sweep a greater swath of sky for a view that covers the largest area possible today.

Keeping it cool

Many onboard space sensors use infrared to create images. That means the sensor cannot exceed the temperature of the object it is imaging to work properly.

Raytheon’s Compact In-line Cryocooler chills the FPAs and optics so they can pick up the right heat signatures from Earth. Additionally, it is smaller and more adaptable than competing technologies.

“Einstein said everything should be as simple as possible, but not simpler,” said Laughrey. “That’s what we’re focused on: taking space optics to the next level by simplifying the way we approach solutions.”