Lara Oliveira, Visiona Space Technology
Mairon Wolniewicz, Visiona Space Technology
Mariana Barbosa, Visiona Space Technology
Lara Oliveira, Space Systems Engineer, Visiona Space Technology
The VCUB1 mission is the first Earth observation and data collection satellite developed by a private company in Brazil, Visiona Space Technology. VCUB1 is a 6U satellite with a 3U primary optical payload, capable of performing TDI images with a swath width of 14 km and a GSD of 3.5 m. As a secondary payload, VCUB1 carries a software-defined radio for ground data collection. The satellite’s onboard data handling and attitude control softwares were fully developed by Visiona, and first tested in orbit with VCUB1.
The mission objective is to validate the payloads, the onboard software, and the attitude control software. VCUB1 was launched in April of 2023 and went through a period of software validation and camera calibration. After the commissioning and the start of the imaging operation, approximately 500,000 km² of images were successfully acquired.
The VCUB1 attitude control subsystem hardware consists of star trackers, sun sensors, magnetometers, gyroscopes, GPS receivers, reaction wheels, and magnetorquers. Several ground and in-orbit tests were performed to validate the functioning of each hardware that composes the subsystem.
As for the attitude control software, ten different operational modes were developed and tested in orbit. Each operational mode has a specific objective, such as the satellite detumbling, nadir pointing with magnetorquers, fine nadir pointing with reaction wheels, pointing of the solar panels to the sun, imaging push broom, pointing to an inertial target and pointing to an Earth fixed target. The navigation, guidance, and control algorithms were developed in MATLAB/Simulink language and coded into C to be embedded in the onboard software.
This article focuses on the VCUB1 attitude control software validation in orbit. Some features of the software are presented along with in-orbit test results that led to the inflight software validation.
A Dynamic Satellite Simulator was used for test planning. In this software, the attitude control algorithm runs along with a simulator of the “real world”, where the time, orbit, and attitude, along with the sensor readings and actuator commands are simulated. This allows every procedure to run first on ground, ensuring the setup is correct before performing any action on VCUB1.
The tests in orbit are performed using the capability of the onboard software to change operational mode and parameters through tables configured on ground and uploaded. During the test, telemetry packets are collected and downloaded. This data is then compared to simulations to ensure that the obtained results are as expected.
Among the tests conducted, the satellite detumbling was successfully checked, lowering its angular velocity to safe values for other modes to operate. The capability of performing nadir pointing within the required specifications was demonstrated using only reaction wheels, magnetorquers, and magnetometer. Fine nadir pointing was achieved using star trackers for attitude determination and reaction wheels for attitude control. Additionally, the satellite successfully pointed to a commanded image target and performed a push broom imaging operation.
From the data collected in these tests, the attitude control software was successfully validated in orbit. The software is capable of performing all the necessary guidance, navigation and control functions for VCUB1, meeting the mission’s requirements.
Having validated the software in orbit during the VCUB1 mission, minor modifications allow the portability for Visiona’s future satellites, with bigger structure and a different hardware architecture. This shows that Brazil, through Visiona, has achieved autonomy on attitude control software development and is ready for the next missions in the upcoming years.