Rocket Lab’s fourteenth Electron launch, “I Can’t Believe It’s Not Optical”, launched on Monday, August 31, 2020, at 03:05 (UTC).

Its payload was the Capella Sequoia, an Earth observation satellite that utilizes synthetic aperture radar. According to Rocket Lab’s press release and mission overview, the satellite can provide “high-quality images of the Earth day or night, and in any weather conditions….providing insights and data that can be used for security, agricultural, and infrastructure monitoring, as well as disaster response and recovery.”

Sequoia is the first in a planned constellation.

A couple of the satellites I’ve mentioned use synthetic aperture radar (SAR) sensors rather than optical sensors. Unlike conventional optical sensors that use ambient light, such as the little camera in your smartphone, synthetic aperture radar emits radio pulses to “illuminate” a target scene and an antenna that is moving (because the spacecraft that it’s attached to is moving) records the time it takes the radar pulses to return. It’s the change in position of the antenna that creates a large synthetic antenna aperture — effectively creating a much larger antenna than the size of the physical receiver. The larger the aperture, the higher the image resolution will be. These systems aren’t affected by things like fog, clouds, or darkness, which can significantly increase the amount of time they can image.

The collected data can be used to create two-dimensional images and three-dimensional reconstructions of objects, such as landscapes. In many ways, SAR and side-scan sonar systems are very similar in that both systems emit the energy used to image the target of interest. A few applications of the technology include sea ice monitoring in the north, disaster response, environmental monitoring for things such as leaking ships and oil wells, topographic mapping, and the tracking of ships.

More Information

Rocket Lab mission page 

Capella Space article 

Spaceflight Now article 

Capella info page (GSP)