How to Deploy and Talk To LEAVES on Venus

We reported before about a NIAC-funded project known as the Lofted Environment and Atmospheric Venues Sensors (LEAVES) mission to study Venus’ atmosphere. While the technology behind the idea is still under development, it has already inspired a team of Worcester Polytechnic Institute (WPI) undergraduates to develop a supporting satellite mission to launch and communicate with the leaves. Their paper, part of their B.S. Thesis, details how to use these new sensors and the challenges ahead.

As a refresher – the main unique selling point of LEAVES is that they are inexpensive ways to collect data about Venus’ atmosphere – at least from the height of about 100km down to 30km, where a lot of interesting atmospheric physics is taking place. They are designed without a propulsion system and, as such, glide down on their own accord, sending back data about the local pressure, temperature, atmospheric composition, and the probe’s orientation via an inertial measurement unit like those used on drones.

They aren’t intended to last long, but the short time they will be present in the atmosphere could provide insights into several outstanding questions about Venus, such as what compound is absorbing near-ultraviolet light in the upper atmosphere or the local carbon monoxide concentration. However, their distribution over the planetary surface is a critical part of any such effort – which is where the mission design from the team at WPI comes in.

Their mission design revolves around two spacecraft joined together for launch and approach to Venus but then breaking apart into wildly different orbits. One of them, Demeter, is responsible for launching the LEAVES. The other, Persephone, is named after Demeter’s daughter, whom Venus’ Greek equivalent had taken away to the underworld. It is left at a higher orbit and responsible for transmitting the data collected by the LEAVES back to Earth.

Demeter had two important design decisions—one was where to deploy the LEAVES, and the second was how to. The team came up with a deployment strategy of eight LEAVES every 20 meters of latitude the entire way around the planet, for a total of 144 probes. Importantly, these would be deployed on the day/night light to examine how the difference between day and night might play a role in the sulfur dioxide cycle on Venus. 

How to deploy them offered a different challenge – the team settled on 18 miniature housings, each attached to a small solid rocket booster using hydrazine. Demeter would orbit around the planet at an altitude of about 235km and would launch eight LEAVES every 20 degrees around the planet. Those LEAVES would descend through the atmosphere – some around the equator, some around the poles – and would deploy their glide form at about 150km from the surface. At around 100 km, they would start sending back data to Persephone, waiting overhead. After its deployment mission was complete, Demeter itself would deorbit and start burning up in Venus’ atmosphere.

Persephone has a much simpler job—it uses a rocket booster to reach a 2000km orbit and patiently waits until the LEAVES are deployed. It then uses a high-gain antenna to pick up signals from the LEAVES’ relatively weak communications systems and stores them on its local hard drive. Once all the data has been gathered, Persephone transmits it back to Earth.

All the components except one on both satellites have very high Technology Readiness Levels (TRL-9). The single exception is the deployment tubes for the LEAVES, which have an expected TRL of 1-2, meaning they would require more development and testing before being ready for prime time.

There is no deadline for that development and testing for now as LEAVES is still just a NIAC project and has not been selected for a mission opportunity to Venus. Given the increasing interest in exploring our sister planet, it seems likely that a similar mission will someday launch – and maybe some of the team that spent so much of their senior year working on this project will have a hand in working on the version that finally does make it there.

Learn More:
Baxter et al. – Design and Analysis of a SmallSat as a Communication Relay for Venus Atmospheric Probes
UT – Floating LEAVES Could Characterize Venus’s Atmosphere
UT – Atmosphere of Venus
UT – Venus has Clouds of Concentrated Sulfuric Acid, but Life Could Still Survive

Lead Image:
Mockup of the Demeter spacecraft, including the deployment tubes for the LEAVES.
Credit – Baxter et al.

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