Delivering better flight software is an important concern to improve CubeSat missions success. It has been identified as a key element to enhance team collaboration, increase reusability, reduce the mission risk, and facilitate the development and operation of new mission concepts, such as satellite mega-constellations. An appropriated fight software architecture represents the functional and non-functional requirements and guides the development. Therefore, to achieve the expected software quality, the architecture should be closely monitored during the entire software life cycle. However, ensuring that a flight software for a spacecraft embedded system closely follows the proposed architecture and addresses the set of non-functional requirements is a difficult and nontrivial problem. Motivated by requirements commonly described in previous CubeSat missions, in this work, we present the design and implementation of a flight software architecture based on the command design pattern. We also present an architecture tracking methodology to verify and control the flight software quality criteria during the development process through the use of graphical software analysis tools and agile programming techniques. This automatic software analysis tool was developed using Git, Jenkins, Moose, and Roassal, and has been applied in the SUCHAI series of nanosatellites to evaluate the impact of the architecture verification during the development history. The implemented flight software and the verification tools have been released as open source platforms and are available for the CubeSat community.

Absolute attitude estimation sensors provide high accuracy pointing capabilities to spacecraft, but as developed thus far, they constitute a large fraction of CubeSat mission’s budget. We introduce SPE Lab Open Star Tracker (SOST), an ultra-low-cost solution that currently provides sub-arcminute precision at a frequency of 1 to 3 estimations per minute in the Lost-In-Space scenario. Our Star Tracker development rests on open source astronomy software, the Raspberry Pi 3 B+, and its camera. We developed a new algorithm to solve the Lost-In-Space problem that works by acquiring an image and comparing it with different stellar catalog segments. We tested our algorithm using images from working satellites. The functioning of our platform was evaluated by using night-sky pictures taken from ground. We also conducted environmental tests of our platform by using a thermal-vacuum chamber. We optimized the catalog segment separation by analyzing the execution time, success rate, precision, and power consumption of the full platform. SOST delivers a mean precision below 1-arcminute for the boresight direction. With a segment separation of 10°, the attitude estimation is found in the 97.3% of the cases with processing time under 20s. The success rate improves to 99.8% by using 5° as segments separation but processing time doubles. This platform is open and freely available to CubeSat researchers interested in further development or deployment.

In this work, we present the positioning error analysis of the 12 May 2021 moderate geomagnetic storm. The storm happened during spring in the northern hemisphere (fall in the south). We selected 868 GNSS stations around the globe to study the ionospheric and the apparent position variations. We compared the day of the storm with the three previous days. The analysis shows the global impact of the storm. In the quiet days, 93% of the stations had 3D errors less than 10 cm, while during the storm, only 41% kept this level of accuracy. The higher impact was over the Up component. Although the stations have algorithms to correct ionospheric disturbances, the inaccuracies lasted for nine hours. The most severe effects on the positioning errors were noticed in the South American sector. More than 60% of the perturbed stations were located in this region. We also studied the effects produced by two other similar geomagnetic storms that occurred on 27 March 2017 and on 5 August 2019. The comparison of the storms shows that the effects on position inaccuracies are not directly deductible neither from the characteristics of geomagnetic storms nor from enhancement and/or variations of the ionospheric plasma.

This article presents a feasibility analysis to remotely estimate the geo-location of a femto-satellite only using two station-CubeSats and the communication link between the femto-satellite and each CubeSat. The presented approach combines the Time Difference Of Arrival (TDOA) and Angle Of Arrival (AOA) methods. We present the motivation, the envisioned solution together with the constraints for reaching it, and the best potential sensitivity of the location precision for different (1) deployment scenarios of the femto-satellite, (2) precisions in the location of the CubeSats, and (3) precisions in each CubeSat’s Attitude Determination and Control Systems (ADCS). We implemented a simulation tool to evaluate the average performance for different random scenarios in space. For the evaluated cases, we found that the Cramér-Rao Bound (CRB) for Gaussian noise over the small error region of the solution is highly dependent on the deployment direction, with differences in the location precision close to three orders of magnitude between the best and worst deployment directions. For the best deployment case, we also studied the best location estimation that might be achieved with the current Global Navigation Satellite System (GNSS) and ADCS commercially available for CubeSats. We found that the mean-square error (MSE) matrix of the proposed solution under the small error condition can attain the CRB for the simulated time, achieving a precision below 30 m when the femto-satellite is separated by around 800 m from the mother-CubeSat.

A 3D-printed multi-sectioned high-gain dielectric resonator antenna (DRA) with a broadside symmetrical radiation pattern is presented. The design consists of a cylindrical DRA operating at 5.8 GHz surrounded by a high-permittivity dielectric ring and a matching ring between them. This new geometry is used to transform the generated standard radiation pattern of the cylindrical DRA into a symmetrical one on both planes increasing the antenna gain. A parametric study is conducted to assess the sensitivity of the parameters of the ring over the symmetry of the radiation pattern highlighting that the same DRA can be used to obtain radiation patterns with different characteristics. The antenna is manufactured using low-cost 3D printing and low-loss dielectric filaments. Measurement results show a good agreement with simulations, achieving a maximum gain of around 12.7 dBi and a symmetrical radiation pattern.

The main effects of the 10 June 2021 annular solar eclipse on GNSS position estimation accuracy are presented. The analysis is based on TEC measurements made by 2337 GNSS stations around the world. TEC perturbations were obtained by comparing results 2 days prior to and after the day of the event. For the analysis, global TEC maps were created using ordinary Kriging interpolation. From TEC changes, the apparent position variation was obtained using the post-processing kinematic precise point positioning with ambiguity resolution (PPP-AR) mode. We validated the TEC measurements by contrasting them with data from the Swarm-A satellite and four digiosondes in Central/South America. The TEC maps show a noticeable TEC depletion (<−60%) under the moon’s shadow. Important variations of TEC were also observed in both crests of the Equatorial Ionization Anomaly (EIA) region over the Caribbean and South America. The effects on GNSS precision were perceived not only close to the area of the eclipse but also as far as the west coast of South America (Chile) and North America (California). The number of stations with positioning errors of over 10 cm almost doubled during the event in these regions. The effects were sustained longer (∼10 h) than usually assumed.