Earth Through a 2-mm Lens From a 6,000 km Orbit

Credit: University of Maribor

The TRISAT-R CubeSat, equipped with a tiny camera, captured a unique image of Earth from 6,000 km, contributing to ESA’s research in medium-Earth orbit and digital imaging effects.

A distant, partly-shadowed Earth, as viewed from a 6,000 km (3,700 mile) altitude orbit. This unusual image was acquired using an extremely miniaturized camera. It measures just 2 mm (0.08 inches), which is about the size of the edge of a 20 euro cent coin (or a US nickel). It is part of a minuscule technology experiment aboard ESA’s shoebox-sized TRISAT-R CubeSat.

TRISAT-R project manager Iztok Kramberger of the University of Maribor explains: “This tiny camera measuring less than two cubic millimeters in size took a picture of an object measuring approximately one trillion cubic kilometers – our beautiful planet Earth – from thousands of kilometers away.”

A CubeSat made from three standardized 10-cm (4-inch) boxes, TRISAT-R is Slovenia’s second space mission, which flew on Europe’s inaugural Vega-C launch last year to the relatively inhospitable environment of medium-Earth orbit, at 6000 km (3,700 miles) up. The mission’s orbital path takes it right through the heart of the ionosphere – an electrically active layer of Earth’s atmosphere – as well as the inner Van Allen radiation belt.

The side cover of the TRISAT-R CubeSat measuring 10×10 cm; and in the middle can be seen its photo diode (the white component in the middle) and the camera (the small black dot adjacent to the diode, directly towards the top of the image). In the center of the camera you can see the 2 by 2 mm lens of the camera, possessing a 120 degree field of view. The lens is made from clear borosilicate glass providing radiation resistance, and is directly mounted on the image sensor below providing 320×320 pixels. Credit: University of Maribor

This allows TRISAT-R to test a suite of radiation-detection payloads. In addition, the TRISAT-R team embarked a pair of tiny cameras, with lenses made from clear borosilicate glass to provide limited radiation resistance, mounted directly onto 320×320 pixel image sensors.

Dr. Kramberger adds: “The resulting picture of Earth is very low resolution as these highly miniaturized cameras were not intended to perform terrestrial imaging, plus TRISAT-R satellite employs magnetorquers for its attitude control, so that precision pointing is difficult to achieve.

“Our main interest has been in capturing examples of the ‘Black Sun effect’ – commonplace in terrestrial digital imaging, where over-saturation of pixels can cause very bright areas to appear dark. We have succeeded in these investigations, but have also been lucky enough to acquire images like these.”

ESA supported the manufacturing, assembly and testing of TRISAT-R through the ‘Fly’ element of its General Support Technology Program, opening up in-orbit demonstration opportunities for European companies.

Located in its unique and challenging orbit, TRISAT-R’s commissioning phase is due to conclude later this month, encompassing 16 months of successful in-orbit operations.