The Guinness Book of World Records has awarded the Japan Aerospace Exploration Agency (JAXA) the official record for the lowest altitude achieved by an Earth observation satellite. During its mission from December 23, 2017 to October 1, 2019, the Super Low Altitude Test Satellite (SLATS) “TSUBAME” reached a suitably super-low altitude of 167.4 km (104 mi).
Earth observation satellites are excellent platforms for learning more about our planet, but what makes them so effective is also one of their major disadvantages. Because they sit in low-Earth orbit at up to 2,000 km (1,200 mi), they can observe large areas of the Earth's surface. Unfortunately, being at such an altitude means that the resolution of the images that can be captured is limited.
The TSUBAME mission was designed to test the feasibility of placing satellites in super-low altitudes between 200 and 300 km (120 and 190 mi), where they can capture high-resolution images. The problem is that the highly tenuous atmosphere at that altitude produces a thousand times more atmospheric drag than higher altitudes, and the atomic oxygen present can cause spacecraft to quickly deteriorate.
To overcome this, TSUBAME was made out of special oxygen-resistant materials and was equipped with an ion engine and gas-jet thrusters to help it maintain orbit and precise positioning so it could capture surface images and measure oxygen concentrations.
During its mission, TSUBAME started at an altitude of 271.5 km (168.7 mi) before lowering to the record 167.4 km, which it maintained for seven days. It managed to both withstand exposure to the atmosphere and capture the desired test images.
"I think we managed to create this unprecedented satellite that is able to maintain orbit in super low altitude, not only because of the systematic and fundamental technologies that we possess to develop and operate artificial satellites, including our many years of experience of the ion engine and the tracking & control technologies, but also because of the high level of science and technology we have in Japan," says Sasaki Masanori, SLATS Project Manage. "I would like to make use of this achievement toward the future science, technology and satellite utilization, and contribute toward helping to solve as many of our social issues as possible."
Source: JAXA