The Xatcobeo Project

satellite

In 2007, the European Space Agency (ESA) opened opportunities to interested parties to launch the first satellite of Vega. One of those selected for the launch is a university project originally dubbed Dieste. The educational project was later renamed Xatcobeo.

The project, a collaboration between the University of Vigo’s Alen Space and Instituto Nacional de Tecnica Aerospacial (INTA), aimed to design and build a CubeSat 1U-type satellite Fernando Aguado Agelet spearheaded the design and construction of the first Galician artificial satellite. Retegal, a corporation owned by the Galician government, supported this non-earth observing mission.

The mission comprised 80 students from various disciplines and ten faculty members who supervised the students. The team was divided into smaller teams to focus on specific critical areas of the project, such as design, engineering, management, and science. INTA provided management and technical support to the team. The project team had to observe ESA’s prescribed standards.

The Xatcobeo project was a part of launching the Vega rocket in Kourou, specifically from the Guiana Space Centre. Its life expectancy was six months to one year, with a project cost of around 1.2 million euros. Spain’s Ministerio de Ciencia e Investigacion funded half of the cost, Retegal took care of 25%, and the University of Vigo and INTA took on the remaining 25%.

How the Project Got Its Name

“Xatcobeo” may seem an unlikely name for a satellite project.

Interestingly, the name has a spiritual background. It is based on a 900-year-old tradition that goes with the Ano Santo Xacobeo, the Galician term for the holy year of St. James, which happens each year when the feast day of St. James falls on a Sunday. According to Catholic tradition, those who visit the Cathedral of Santiago de Compostela in Galicia are given jubilee indulgence during this special year.

Those involved in this University Of Vigo CubeSat project made a play on the famous Xacobeo by inserting the letter “T” to make the first syllable sound like “SAT.”

The Objectives of the Mission

vision

The mission’s main objective was to further the participating students’ education by giving them access to space, allowing them a once-in-a-lifetime experience. Participating students and faculty can improve their skills and knowledge in communication engineering, electronics, and software development through the project.

Besides that, the project intended to perform experiments that involved the following:

  • Radiation Displacement Damage Sensor (RDS)
  • Software-Defined Reconfigurable Radio (SRAD) system
  • Solar Panel Deployment Mechanism (PDM) system

Radiation Displacement Damage Sensor

This experiment attempted to verify the usefulness of RDS, a device that detects and measures the amount of ionizing radiation that an object, person, or space has been exposed to. The sensor is based on a semiconductor, silicon diode, developed to measure the kinetic energies of fast neutrons and similar heavy particles.

The resulting satellite from the Xatcobeo project was launched into a non-typical low Earth orbit, giving RDS a one-off occasion to monitor the radiation in that area.

Software-Defined Reconfigurable Radio

coding

The project team hoped to establish communications with this new radio system that uses a field-programmable gate array (FPGA). They also hoped to alter the built-in modulations and still have that communication link.

At the time of the experiment, this radio system was seen to play a crucial role in future space missions because of its ability to redefine a post-launch communication system.

Solar Panel Deployment Mechanism

The experiment wanted to test if the mechanism could provide additional electric power if deployed properly. With additional power, Xatcobeo’s life expectancy will be extended, and the spacecraft’s performance will be improved.

The experiment’s success would have benefited future space missions with more refined and better-powered payloads.

The Challenges

Since the project team consisted of students with diverse backgrounds, working together proved challenging. Apart from learning how to adapt to each other, students had to grapple with the standards and work methods prescribed by ESA.

For instance, the CubeSat standard requires a small-scale satellite that measures 10 cm x 10 cm x 10 cm, with a weight not exceeding one kilogram. The deployment mechanism had to fit in a casing that measures 82.6 x 98 mm x 6.5 mm. The team had to ensure they used built-in components that were as light and small as possible.

The materials used must be able to avoid the possible threats posed by electrostatic discharges produced by a high ion-density atmosphere. They must survive the different types of radiation existing in the working environment and the changes in temperature as the satellite orbits in and out of sunlight.

Additionally, the antenna must be insulated from the satellite metal to prevent short circuits and positioned at a 45-degree angle to the adjacent edge.

The team had to design the PDM such that the weight of deployable parts is kept to a minimum and all systems fit into a 6.5 mm envelope.

The Spacecraft Design

Uses of Polyamide

To satisfy the ESA standards, the project team used polyamide, a polymer material coated with zinc- or silver-based dissipative paint on the support mechanism or sub-chassis to insulate the antenna.

The polyamide also provided an acceptable level of resistance to radiation and stability versus external temperature changes. The stability avoids tension at the attachments’ mechanical interfaces in case of dilations and contractions. The material also reduced the structure’s fragility, avoiding vibrations that can interfere with a successful launch.

Using polyvinyl acetate adds protection to the antenna. It shields the outer part of the antenna, retaining its shape when it needs to be folded. The sheet also prevents the antenna from any static interaction.

Titanium Gr5 M2 nuts and bolts were also used with high-strength materials for the attachment elements to make the structure small and lightweight.

Three other subsystems were crucial to making the satellite work. These are:

  • Electrical Power Subsystem (EPS)
  • On-Board Data Handling Subsystem (OBDH)
  • RF Communications

Electrical Power Subsystem

This system used around 3W of power from triple-junction solar cells. A UK-based company, Clyde Space, provided the power. Spectrolab, a Boeing company, provided the ultra triple junction (UTJ), with the Li-ion battery having a capacity of 1250 mAh.

On-Board Data Handling Subsystem

The OBDH subsystem comprised an On-board Computer(OBC) and an On-board Programmable Interface Controller (OBPIC). The OBC is based on a Virtex II-FPGA; OBPIC regulates the payload power and primes the bus system. The project team conveyed on-board data through the I2C bus.

RF Communications

XaTcobeo’s CubeSat downlink transmissions used UHF bands of 437 MHz, Manchester pulses (SP-L), and a data rate of 1.2 kbit/s or only 12.5% of the system’s maximum capability. Its uplink used VHF bands of 145 MHz. The transponder used a phase with a data subcarrier (PM/PBSK).

The CubeSat also used a Terminal Node Controller (TNC) and four Marconi or monopole antennas to receive and send data.

The XaTcobeo Launch

earth

A multiple payload launch happened on February 13, 2012, in Kourou, French Guiana. The primary payload was the Laser Relativity Satellite (LARES) weighing 400 kilograms. CubeSats sponsored by ESA were launched as secondary payloads using a poly picosat orbital deployer (P-POD).

ESA limited the secondary payloads to universities that could comply with the documentation and CubeSat requirements. The first Spanish CubeSat, XaTcobeo, was among the secondary payloads. The launch happened after more than three years of the project team’s rigorous work.

Below is a list of the other CubeSats that launched as secondary payloads. Each CubeSat had its unique mission.

  • ALMASat
  • e-st@r
  • Goliat
  • MaSat-1
  • PW-Sat
  • Robusta
  • UniCubeSatGG

ALMASat

ALMASat, or Alma Mater Satellite, was a microsatellite by the University of Bologna. The Italian Ministry of Research funded it. Its mission was to test the 3-axis pointing accuracy.

e-st@ar

Developed by the Politecnico di Torino, e-st@r is a mini satellite whose mission is to determine the capability of the autonomous attitude control system.

Goliat

The first artificial Romanian satellite developed by the University of Bucharest produced an Earth surfacing image with a 3-megapixel digital camera and measured the amount of cosmic radiation and micrometeoroid.

MaSat-1

This CubeSat, Magyar and Satellite, is a product of Hungary’s Budapest University of Technology and Economics. Its mission was to demo different spacecraft avionics, such as power conditioning systems.

PW-Sat

PW-Sat was built by the Warsaw University of Technology in Poland. Its unique mission was to test a de-orbit technology.

Robusta

Radiation on Bipolar for University Satellite Test Application (ROBUSTA) is a CubeSat developed by France through the University of Montpellier. Its mission was to test the effects of low radiation dose rates on bipolar transistors.

UniCubeSatGG

This was the first CubeSat mission of “la Sapienza” of the University of Rome. It aimed to study the enhancement of gravity gradient through a deployable boom.

The Mission Status

The mission ended in the early afternoon of August 13, 2014, after it disintegrated over Australia.

A few hours after its launch, the ground station at the University of Vigo received signals from XaTcobeo. The signals indicated that the telecommand systems and telemetry were properly functioning.

In March 2012, the Spanish CubeSat’s operations experienced unexpected interferences. However, it continued to transmit telemetry data to the ground station.

During its lifetime, which lasted about 30 months, Xatcobeo completed more than 13,600 orbits around the Earth.

Professor Fernando Aguado Agelet has moved on to become an International Academy of Astronautics (IAA) member. One of the mission’s participants, Alberto Gonzales, is now the Chief Technology Officer of Alen Space, an aerospace company founded in 2017 as a university spin-off.

A Sense of Fulfillment

Despite the roadblocks they experienced, the team members found the project a rewarding experience.

They valued the amount of learning they acquired as they got acquainted with and applied the technical concepts of building the various parts of the spacecraft. Besides the technical knowledge, they also appreciated the soft skills they developed throughout the project. These skills included communication, organizing, and project management skills.

Moreover, working in teams helped them develop satisfying personal relationships that extended beyond the project. The discipline and the camaraderie that was developed during the project resulted in each member committing to help on succeeding projects.

Moving Forward

The Xatcobeo mission might have ended in 2014, but it doesn’t mean that the interest in satellite missions died with it.

The mission sparked more interest in small satellite technology, with many countries showing interest in building and strengthening their space capacity-building programs. However, the CubeSat or small satellite missions have evolved significantly over the years.

Satellite missions, which were once intended for educational and training purposes, are now more operation-oriented. CubeSats are no longer opportunities for students who want to gain experience and exposure in space systems. Cubesats are now being built for scientific missions and services.

More mature organizations take on commercial missions, which can potentially transmit a massive volume of data to the ground station. That being the case, the documents that outline the thought process of the Xatcobeo team in designing the spacecraft and the data transmitted during launch will be an ideal takeoff point for those gearing up for similar missions.

While it might seem easier to adopt the latest technology in designing CubeSats or small satellites, there is wisdom in learning from the experience and expertise acquired from previous missions like Xatcobeo.

The Xatcobeo mission used commercial-of-the-shelf (COTS) technologies to perform complex functionalities while keeping the structures simple and low-cost. It also observed the strict standards on the spacecraft’s weight and size — light and small, which is not typical of the traditional spacecraft blueprint.

The disparity challenges players of new satellite missions to integrate the best of both worlds. They can do this by leveraging the miniaturization of electronic devices and learning from Xatcobeo’s calculations of the various parameters for developing the spacecraft.