In the course of this project, the Qarman team is facing some major technical challenges which, if tackled successfully would mean a major breakthrough in the CubeSat society. Some of these challenges are briefly recapitulated hereunder:
The Thermal problem: Most electronics are intended to be used in a temperature range between 0-70°C. Space, however, is at the same time a very cold (when eclipsed from the sun) and hot (when facing the sun) environment. This means that electronics often need to be heated up to avoid freezing. However, since Qarman acts both as a satellite and as a re-entry vehicle, the same electronics must be shielded against the harsh thermal environment during the re-entry. During this stage of the mission, the environmental conditions are such that the satellite is surrounded by a plasma hotter than the sun. Temperature gradients are expected to be as high as 1000°C over a few mm only. Understandably, it took the team several months to simulate the problem and find solutions for it.
The communication problem: It is well known that during re-entry radio communication is impossible. This is due to the fact that the satellite is surrounded by free electrons which shield, reflect and/or attenuate electro-magnetic radiation. In practice this means that scientific data obtained during the re-entry phase cannot be sent to ground in real-time, but must be stored until the radio black-out period is over. All data must be retrieved in the short time window between the end of the black-out and the crash of the satellite. Put differently, 20 minutes worth of data must be sent in less than 5 minutes. To tackle this problem, data must be compressed and broadcasted in a certain order of priority, such that we are able to receive the most important data first.
The stability problem: The satellite caries no active de-orbiting device (such as an engine), so the only way to slow it down (and to make it plunge back into the atmosphere) is to increase the atmospheric drag using the AeroSDS panels. However, these panels should be at the same time light, thin, strong and thermally robust enough to withstand the high aerodynamic loads at high temperatures during the re-entry. If for some reason one of the panels would deform or break off during the re-entry, then the satellite would start to tumble fast, exposing parts to the stagnation heat that are not designed for this, with predictable results. The design and simulation of these panels is therefore of utmost importance for the success of the mission.
For more information on QARMAN, contact the QARMAN team: This email address is being protected from spambots. You need JavaScript enabled to view it.
The QARMAN team underlines the importance of scientific education for children (8 to 18 years). Therefore, we are open for participation and advice in educational projects and/or debates in the framework of satellite building and space science in general. Feel free to contact us! Questions from individual children or school projects can be answered in English, French, Dutch.
Current Team
Amandine Denis is a system engineer at the von Karman Institute. She acts as the project manager of QARMAN.
Damien Le Quang acts as coordinator of the project.
Rémy Vostes and Jimmy Freitas Monteiro are responsible for the operations.
Terence Boeyen is a watchmaker by trade, and handles fine adjustments on the mechanical parts of the satellite.
ITP Engines UK is kindly sponsoring QARMAN with the licences for the thermal analysis and simulation software https://www.esatan-tms.com
QARMAN Flight Scenario
The flight scenario of QARMAN is shown the figure above. There are 5 phases planned for the mission:
Phase 0:
Right after deployment at an altitude of 380 km starts the commissioning phase, during which the on-board computer is booted, the UHF/VHF antennae are deployed and all systems are checked (For safety reasons during launch the batteries are fully charged but all systems are switched off to avoid electro-magnetic interference with the launcher telemetry). It is expected that QARMAN will tumble after deployment at a rate of lower than 10 degrees per second. Using a combination of inertia wheels and magnetorquers, the satellite will be stabilized or detumbled. This phase is expected to last three days, after which QARMANs attitude should be known within 2 degrees of uncertainty.
Active systems are OBC, UHF modem, ADCS and EPS
Phase 1:
During phase 1, which lasts about one month, the satellite will attempt to “chase” a target satellite by controlling the surface exposed to the residual atmosphere. This is done by altering the angle between the satellites principle axis and the direction of flight, thus controlling the atmospheric drag which experiences the satellite. This is possible because, contrary to popular belief, there is still a residual atmosphere, even at altitudes above 300 km. Indeed, the atmospheric pressure at this height (in the so-called thermosphere) is slightly less than 0.1Pa, or one millionth of the atmospheric pressure at ground level. Thus, by changing QARMAN’s attitude, it is possible to change its drag force. This force is used as a propulsive means to control the trajectory, and to come as close as safely possible to a target satellite (or a virtual target). During the phase 1 the solar panels will be kept in stowed configuration (as shown below), in order to keep the inertia low to be able to steer the satellite with on-board actuators.
Active systems are OBC, UHF Radio, GPS, ADCS and EPS
During this phase, the AeroSDS panels are in folded configuration, as shown in the following figure.
Phase 2:
At the end of phase 1, the satellite is expected to have an altitude of 320km. Upon completion of the Differential Drag experiment, the side panels will open to rest at an angle of 15 degrees with respect to the satellite axis. This results in an increase of aerodynamic drag, thus a decrease of velocity. Hence, the satellite will slowly de-orbit.
Active systems are: OBC, UHF Radio, ADCS, GPS, EPS and AeroSDS
The following figure shows the satellite with deployed panels.
Low-power mode (LPM):
This phase is placed between phase 2 and 3 to prepare the satellite for re-entry, where the unnecessary sub-systems will be switched off. The satellite will cool down and the batteries will be charged in order to survive during re-entry.
Active systems are: OBC, UHF Radio, ADCS and EPS
Phase 3:
Phase 3 is the re-entry part of the mission where various sensor data will be acquired, processed and logged. This is the most critical part of the mission, as the satellite is subject to very high temperature and hypersonic velocities. Gas temperatures around the satellite are expected to exceed 10000K (more than 50% hotter than the surface of the sun.), while the satellite flies through the upper atmosphere at Mach 27. To protect the electronics during the re-entry, several layers of high-tech insulation (so-called Aerogel) and special ablative material are implemented on the satellite. Due to the extremely high temperature, a cloud of free electrons exists around the satellite. As a consequence, no data can be transmitted during the re-entry. This is the infamous “black-out window”. Instead, the acquired data is stored on a flash disc, and the compressed data is to be transmitted once the blackout has terminated (at an altitude of around 45 km), towards the Iridium constellation. The data budgets are calculated such that all data can be safely transmitted in the short time frame between the end of the black-out window and the satellites’ crash on ground. After the phase 3 QARMAN will safely crash-land on ground, providing valuable data for future atmospheric research.
Active systems are: OBC, Iridium Modem, XPL and OBC Survival Units, XPL and AeroSDS
QARMAN uses UHF amateur radio band as coordinated by IARU and notified to ITU. It will be used for transmitting a beacon all around the word, and exchanging telecommand and telemetry over VKI ground station (or possibly other partner stations).
QARMAN team would be glad to receive support from the ham community for beacon reception. Details are as follows:
Frequency: 437.350 MHz (as coordinated by IARU)
Periodicity: every 2 minutes in nominal modes (Phase 0, Phase 1, Phase 2); every 10 minutes in Safe Mode and Low Power Mode.
Modulation: GMSK, 9600 bd
Protocol: AX.25 (UI frames)
Content (information field): 74 bytes in Phase 0, Phase 1, Phase 2, Safe modes; 39 bytes in Low Power Mode. The content of the beacon is defined in the attached document.
From: ON05BE
To: ON4VKI
Space segment transceiver: Li-100 (Astrodev)
Please be aware: we have a frequency buddy! Coincidentally, Phoenix CubeSat will use the same frequency as QARMAN, and be released from the ISS 90 minutes earlier. QARMAN and Phoenix CubeSat will have very similar orbits and might be very close from each other in the beginning. More info about Phoenix CubeSat and related amateur operations can be found here.
