These Raspberry Pi-Powered "Data Recovery Systems," Flown on a NASA Balloon, Deliver Data by Airdrop
With five 1TB microSD cards, foam for protection, and onboard batteries, these data drop-boxes can save astronomical data from destruction.
When NASA is lofting a "super-pressure balloon" skyward in order to capture astronomical imagery from above 99.5 per cent of the Earth's atmosphere, you need a way to get a lot of data safely back to ground — and researchers figured the best way was with a payload package driven by a Raspberry Pi single-board computer.
"In April 2023, the superBIT telescope was lifted to the Earth's stratosphere by a helium-filled super-pressure balloon to acquire astronomical imaging from above (99.5 per cent of) the Earth’s atmosphere," the team responsible for the data recovery project explains.
"It was launched from New Zealand and then, for 40 days, circumnavigated the globe five times at a latitude 40 to 50 degrees south. Attached to the telescope were four 'DRS' (Data Recovery System) capsules containing 5TB solid state data storage, plus a GNSS [Global Navigation Satellite System] receiver, Iridium transmitter, and parachute. Data from the telescope were copied to these, and two were dropped over Argentina."
The problem the DRS hardware was designed to solve is simple: the telescope generated too much data to be easily transferred wirelessly, but its descent post-capture was not expected to be a gentle one — an expectation which proved prescient when the telescope, its balloon deflated, destructively crash-landed at the end of its mission. The solution: multiple redundant capsules which can be ejected, each with a copy of the data and a means to locate it post-landing.
The current-generation DRS is built around a Raspberry Pi 3 Model B single-board computer, the team explains, powered by the main balloon payload while tethered then by two internal 9V lithium batteries when released. Enclosed in a 3D-printed shell with foam for impact resistance and a small level of waterproofing, the Raspberry Pi reads data from the telescope over Ethernet and writes it to five 1TB microSDXC cards.
When triggered, a DRS detaches from the balloon and begins its descent slowed by a parachute. The onboard GNSS receiver tracks its location and transmits this to the ground team. While the tracking system on both jettisoned DRS units failed to track their journey to the ground, the team admits, both began transmitting their location post-landing — and triggered an audible sounder on the carrier board, making it easier to find them on the ground.
"We recovered identical copies of all the data from both released DRS capsules and later from the unreleased DRS and the main data store on superBIT (which also had slightly more telemetry data)," the team writes. "However, superBIT had been completely destroyed upon landing, when its parachute failed to detach (perhaps because of similar thermal issues as the DRS capsules; analysis is ongoing), and it was dragged for 3km through similar terrain, leaving a trail of debris.
"It is, therefore, remarkable luck that superBIT’s solid-state hard drive was later discovered intact," the team concludes. "We did not need it because data had already been retrieved from the released DRS capsules, but having the original copy enabled us to verify that no data on the SD Cards were corrupted."
The team's experience with the DRS system has been published in the journal Aerospace under open-access terms; the hardware design is published to GitHub under the reciprocal Creative Commons ShareAlike license, while a Python tool for simulating balloon trajectories is available under the GNU Lesser General Public License 3.