BEESAT 14-15 Spacecraft

Formation flying and multispectral camera.

Perform formation flight maneuvers there. The primary mission goal is to fly a helix orbit. The satellites can be moved anywhere on their tracks to change the distance and to demonstrate different application scenarios. As part of the mission, further formations will be taken, in which one satellite will autonomously maintain its relative position to the second.

As a payload, each satellite will fly a camera system with four narrowband spectral channels, both of which may be equipped with different optical filters. This would allow for a wider range of scientific data. The camera system is calibrated radiometrically, the ground pixel resolution is 39 m with a windrow width of more than 160 km in a 575 km SSO. An X-band transmitter is used to download all generated data.

 The objectives of the NanoFF mission can be divided into the two groups of research and education. Research and experiments: The primary mission objective of NanoFF is the in-orbit demonstration of formation flight with two 2U-CubeSats. To achieve this, each satellite is equipped with a resistojet propulsion system for orbit control. For navigation, redundant GNSS receivers will provide position and velocity data of the satellites that is used to precisely determine their orbits. The payload of each satellite is a multi-spectral camera system with four spectral channels that are operated in the visible and near-infrared spectrum and is used to demonstrate Earth observation applications in a close formation of two satellites. The research activities are not aiming to sell data or provide commercial services, they are solely conducted out of research interest. It is planned to offer transmissions of compressed pictures in the UHF band to incorporate the amateur radio community into the reception of camera data. Education: TUB actively trains and educates researchers and students in satellite operations in a handson fashion. Especially, the student group “StudOps” of TUB will be highly involded into the operations of the NanoFF satellites. New amateur radio operators are trained within this group as it was done in previous missions of TUB. The amateur UHF communication system will be used for this purpose. UHF operations will be carried out by amateur licensees under their supervision using educational licenses. Part of the operations will be conducted in lectures on satellite operations. The amateur radio club “AfuTUB” of the university will be involved in technical aspects like setting up amateur radio ground stations and working on encoder/decoder software and also providing lectures on this topic to students. Technology research will be published publicly in form of papers and web articles. The tools for encoding and decoding of the communication protocol, called “Mobitex” as used in previous missions of TUB, are available under https://git.tu-berlin.de/rft/com/mobitub-2 The education of students and new amateur radio operators in lectures and as part of the student group “StudOps” are an essential part of this mission. Furthermore, education is implemented through student theses in development and operations. It is planned to transmit compressed pictures of the cameras in the UHF band to incorporate the amateur radio community in the reception of this data. Transmissions shall be announced in advance on the Internet on appropriate platforms like social networks to allow for preparation of the reception. Furthermore, the NanoFF mission provides the platform to conduct intersatellite link (ISL) experiments with the UHF transceivers of both satellites. At TUB, a student experiment is currently being prepared to use the ISL for experiments with radio amateurs. The aim is to test the range of the ISL and at the same time distribute data packets via the satellites that radio amateurs send to one of the satellites.

After the two satellites were ejected, the operations team from the Chair of Space Technology carried out the commissioning phase, during which the individual systems were switched on, tested and put into operation step by step. Since the separation of ION, the satellites have been slowly moving away from each other, as expected.

To achieve the mission objective of formation flight, this drift must be reversed to reduce the distance between the two spacecraft. The team successfully performed two thrust maneuvers with NanoFF B, the satellite that is shown in the video. The orbit has successfully been raised by around 120m. Further maneuvers are required to stop the drift completely and will be carried out over the next few weeks.

After NanoFF-B’s deployment on January 10, 2024, B-Dot was activated within 24 hours, effectively reducing the total angular rate from 8 °/s to under 0.5 °/s within just one orbit (see fig. 8). Following NanoFF-A’s deployment on January 15, 2024, the total angular rate was approximately 5.8 °/s. Over the course of 3 weeks, natural damping gradually decreased this to around 4 °/s. Subsequently, after B-Dot activation, the angular rate was further reduced to approximately 0.5 °/s within half an orbit (see fig. 9). Despite the discrepancies found between design and measured coil parameters, the data from the detumbling of the two spacecraft shows that they are performing well on orbit, which we take as a further confirmation for the successful optimization.

In July 2024, finished the first software upload to our satellites. Both of them now have an updated 𝗔𝘁𝘁𝗶𝘁𝘂𝗱𝗲 & 𝗢𝗿𝗯𝗶𝘁 𝗖𝗼𝗻𝘁𝗿𝗼𝗹 𝗦𝘆𝘀𝘁𝗲𝗺 (AOCS) software with new features that help us with experiments and operational efficiency. The upload process was shortened significantly by compressing the image on ground and then decompressing it on the satellite after reception. Doing so, we were able to achieve an image size reduction of over 38%. Uploading the image took less than 3 days per satellite.

• The new AOCS update includes:
• Introduction of a new precise, numerical orbit propagator which considers perturbations due to the non-spherical Earth and atmospheric density. This will be used for long-term position estimation in case of a loss of GNSS 3D fix and running experiments in orbit.
• The AOCS node on each satellite now forwards the position/velocity of both the satellites to the Formation Flight Computer. With this update we were able to calculate the relative orbital elements (ROEs) of the satellite formation in real time on-board the satellites (using TLEs) for the first time (see image below).
• Improve the accuracy of our GNSS navigation solution data
• Several convenience functions & telemetry to improve operational efficiency & stability