The need to understand our atmosphere

WE BETTER KNOW MARS ATMOSPHERE THAN EARTH…

The latest valuable scientific data of the earth’s atmosphere’s upper layers (exosphere) composition was recorded back in 1983 and performed with now-outdated technology, with modest sensitivity thus leading to poor-quality measurements.

However, the need for reliable data is becoming more and more pressing in the scientific community: such measurements would allow a better understanding of global warming, as well as a better anticipation of the aerodynamic drag at orbital altitudes.

To answer these needs, UniBe invented a state-of-the-art, 10-cm-class low cost time-of-flight mass spectrometer: the CubeSatTOF. It fits into 1 unit of a CubeSat (⅓ of the total CHESS satellites volume). Our challenge is to fly 2 of this CubeSatTOF on different orbits to get a global understanding of the exosphere

twin satellites, differents orbits

The CHESS mission is designed around two identical 3U CubeSat, a modular standard for satellite where 1 Unit is a cube of 10cm. In our case each satellite is 10x10x30cm.

One satellite will be on a 550km high circular orbit and the other on a 400-1000km elliptical orbit. The launch is targeted for Q4 2023, and the scientific mission will run for 2 years.

Thanks to this design we will be able to measure Earth’s atmosphere chemical composition and its evolution over time. We will be able to understand the variations of composition and their driving mechanisms, and finally we will prove that such low-cost and minuaturized equipement could have a major impact for planetary research.

Technical data

CHESS CubeSats are designed around flight proven components as well as in-house developped modules. Exhaustive testing is conducted on each system to minimize mission failure.

The Attitude Determination and Control Subsystem (ADCS) is responsible for the determination and the control of the satellite’s orientation in space. It’s able to orient the satellite in a desired way. 

The orientation can be determined by the sensors that are on the satellite (such as sun sensors, magnetometers,  earth IR sensors). Once we know the orientation of the satellite, we change it by using a set of actuators (3-axis reaction wheels, 3-axis magnetorquers ). By this way the satellite can also change its mode without any command sent from the ground station, for example upon reaching a certain point, the satellite will orient itself towards the Earth to send data.

For the ADCS subsystem we used commercial (off-the-shelf) components, therefore most of our work focuses on testing different flight scenarios and seeing if we can reach the desired attitude for all possible flight cases.

The On-Board-Computer (OBC) controls all the subsystems, collects their data and redirects it to the ground station. It connects to the other subsystems via multiple communication pathways (busses) controlled by a microcontroller or a processor using peripherals. It’ll also implement failure management to keep the satellite alive.

It touches quite a lot of different domains  with the most important ones being electronics, hardware design and embedded programming.

The final design depends a lot on whether or not we’re flying a housemade or a commercial off the shelf OBC. That’s why we are implementing a prototype of our housemade OBC and evaluating a commercial solution.

The role of the Electrical Power System (EPS) is to generate, store and distribute the electricity produced by the solar panels.

It’s core component is an electrical power supply which is a power distribution unit. It’s composed of three modules which are the power control circuit, the photovoltaic panel and the battery. 

It’s an essential and critical subsystem in the cubesat, allowing for the generation, management and distribution of energy to all of the components. That’s why it is important to test the board, the batteries and the solar panel deployment system to make sure everything is well configured and ready to fly.

Finally an estimation of State of Charge for the batteries should be made to ensure that the system lasts the full 2 years of the Mission.

CHESS satellite offers a Radio-Amateur transponder, allowing hobbyist to communicate overseas, using the satellite as a radio relay. A UHF transceiver is also installed, and allow us to communicate directly with the On-Board-Computer, for updates and instructions.

The X-band module offers a much bigger bandwidth than the UHF communication system. This module is dedicated for scientific data transmissions, such as GNSS position or CubeSatTOF analysis.

A high-precision multi-GNSS developed by ETHZ, measuring the total electron content in the ionosphere and air density in the exosphere.

A compact high-performance time-of-flight mass spectrometer. It will measure the chemical composition of the Earth’s atmosphere, including neutral species and ions.

The Attitude Determination and Control Subsystem (ADCS) is responsible for the determination and the control of the satellite’s orientation in space. It’s able to orient the satellite in a desired way. 

The orientation can be determined by the sensors that are on the satellite (such as sun sensors, magnetometers,  earth IR sensors). Once we know the orientation of the satellite, we change it by using a set of actuators (3-axis reaction wheels, 3-axis magnetorquers ). By this way the satellite can also change its mode without any command sent from the ground station, for example upon reaching a certain point, the satellite will orient itself towards the Earth to send data.

For the ADCS subsystem we use commercial (off-the-shelf) components, therefore our work focuses on testing, theoretical simulations, and in-house developement of algorithms.

The On-Board-Computer (OBC) controls all the subsystems, collects their data and redirects it to the ground station. It connects to the other subsystems via multiple communication. It’ll also implement failure management to keep the satellite alive.

The main OBC of the CHESS mission will be a commercial product with an in-house flight software running on it.

Our work here focuses on software developement, integration, and testing.

The role of the Electrical Power System (EPS) is to generate, store and distribute the electricity produced by the solar panels.

It’s core component is an electrical power supply which is a power distribution unit. It’s composed of three modules which are the power control circuit, the photovoltaic panel and the battery. 

It’s an essential and critical subsystem in the cubesat, allowing for the generation, management and distribution of energy to all of the components. That’s why it is important to test the board, the batteries and the solar panel deployment system to make sure everything is well configured and ready to fly.

Finally an estimation of State of Charge for the batteries should be made to ensure that the system lasts the full 2 years of the Mission.

Additional to the main OBC, which will be commercially bougt we will carry an in-house on board computer for in orbit validation.

This OBC is based on a FPGA in combination with a microcotnroller. This setup allows us to update the software and parts of the hardware (FPGA) in flight. This ensures maximal flexibility after launch.

After a successfull in-orbit validation, this OBC can be used as the main computer on other cubesat missions.

Do not hesiteate to reach out to us if you’re interested in the design.

The CHESS mission relies on X-band for science data downlink as it offers a much higher datarate than e.g. UHF.

The transmitter is a commercial sollution while the antenna is developed by our partners from Hochschule Luzern.

A high-precision multi-GNSS developed by ETHZ, measuring the total electron content in the ionosphere and air density in the exosphere.

A compact high-performance time-of-flight mass spectrometer. It will measure the chemical composition of the Earth’s atmosphere, including neutral species and ions.

We use a commercial UHF transmitter  for command and telemetry up- and downlink.

Our activies on UHF focus around simulations, testing, and the developement of a mobile ground station.

The Missions source of power is solar energy captured by solar panels. We rely on commercial panels for the main power production.

Additionally, we test some solar cells for our partner RUAG.