AAUSAT3
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AAUSat-3, (Aalborg University CubeSat-3), is the third
CubeSat A CubeSat is a class of miniaturized satellite based around a form factor consisting of cubes. CubeSats have a mass of no more than per unit, and often use commercial off-the-shelf (COTS) components for their electronics and structure. CubeSats ...
built and operated by students from the
Aalborg University Aalborg University (AAU) is a Danish public university with campuses in Aalborg, Esbjerg, and Copenhagen founded in 1974. The university awards bachelor's degrees, master's degrees, and PhD degrees in a wide variety of subjects within humanitie ...
in
Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of Denmark , establish ...
. It was launched on 25 February 2013 from the
Satish Dhawan Space Centre Satish Dhawan Space Centre - SDSC (formerly Sriharikota Range - SHAR) is a rocket launch centre ( spaceport) operated by Indian Space Research Organisation (ISRO). It is located in Sriharikota, Tirupati district of Andhra Pradesh. Sriharikota ...
in
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
on a
Polar Satellite Launch Vehicle The Polar Satellite Launch Vehicle (PSLV) is an expendable medium-lift launch vehicle designed and operated by the Indian Space Research Organisation (ISRO). It was developed to allow India to launch its Indian Remote Sensing (IRS) satellites ...
(PSLV)
launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload ( spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and ...
(PSLV-C20). AAUSat-3 carries two Automatic Identification System (AIS-1 and AIS-2) receivers as the main payload.


Educational objective

The primary purpose of satellite construction at University of Aalborg is to give the students engineering experience beyond what is normally achieved within a master's degree program. The design, implementation, and manufacturing were carried out by students, with only two exceptions: the manufacturing of the mechanical structure (carried out by the department workshop in alu7075), and the raw non-mounted PCBs. The project is funded mainly by Aalborg University and by Danish Maritime Safety Administration (DaMSA ), along with other sponsors.


Scientific objective

The purpose of the satellite project was to find out if it was possible to receive Automatic Identification System (AIS) signals from a 1U CubeSat. The spacecraft was designed to operate on a non-centralized basis so it would be able to continue functioning even when certain subsystems failed. It carried two automated identification system (AIS) receivers - one based on SDR principle. The images recorded by the satellite were later transmitted to the ground station located at Aalborg University, from which they were made accessible for the general public.


History

Student satellite activities at Aalborg University (AAU) started in 2003 as a result of AAU's involvement in the first pure Danish research satellite, Ørsted, which was successfully launched in 1999. AAUSat-3's predecessors were
AAU CubeSat AAU CubeSat was a CubeSat built and operated by students from Aalborg University in Denmark. AAU CubeSat was launched on 30 June 2003 from the Plesetsk Cosmodrome on a Russian Rockot launch vehicle. The satellite was alive for two and a half ...
(launched in 2003), and AAUSat-2 (launched in 2008). Students from AAU also participated in
SSETI Express The Student Space Exploration & Technology Initiative (SSETI) is a unique project put into execution by students from different universities spread over European countries. In collaboration with space industry they aim to build microsatellites tog ...
(launched in 2005), a student satellite initiative by European Space Agency (ESA) Education. The construction of AAUSat-3 began in the fall of 2007. The satellite prototype was tested on a stratospheric balloon flight in October 2009 as part the BEXUS (Balloon Experiments for University Students) program, which allows European students to test scientific experiments in high altitude conditions. The balloon test served as an excellent opportunity to test the AIS receivers with an extended field of view (FOV) and to acquire realistic samples for further development of the final payload receivers. The payload on BEXUS was called NAVIS (North Atlantic Vessel Identification System).


Operations

AAUSat-3 was launched on 25 February 2013 on PSLV-C20. Operations were a success. 9,000 AIS messages were received on a daily basis and downloaded to the mission control center (MCC), located in Aalborg, Denmark. All subsystems were tested and running. The first 100 days of operation were very successful. No degradation of the satellite was observed, all subsystems were working, and the primary payload – an AIS receiver – was working correctly. Two critical situations occurred during the first 100 days: 28 February 2013 at 06:08: The last message for some days was received. During the previous 24 hours, battery voltage was decreasing, and temperature readings indicated that AAUSat-3 was steady pointing the side without solar cells towards the
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
. During the last pass over Aalborg, it was observed that battery voltage was slowly decreasing. The situation was discussed and analyzed during the day, and it was decided to instruct AAUSat-3 on all upcoming passes to switch off beacon mode because it was using power. No further attempt was taken to make contact during the weekend in order to preserve and recharge the satellite's battery. All passes were supervised. There was total silence until 4 March at 17:52 where the ground station in Aalborg requestes and received a beacon. The beacon showed an uptime of 1 day 19 hours, that everything was working, and that more than 7,000 AIS messages had been received. Everything went back to normal. The requested beacon also showed a high number of reboots, possibly due to low battery voltage. Due to this event, AAUSat-3 was set to tumble slowly – 2 rotations for every 100-minute orbit – to avoid a repetition of the problem. 24 May 2013: The power system (EPS) on AAUSat-3 rejected multi-frame communication packages from the ground. During four passes (500 minutes), the students analyzed the situation and inspected the C source for the EPS server, and a solution was found. A new package was sent to AAUSat-3, and normal EPS operation was re-established. During the event, the rest of the satellite – due to the decentralized design – was working. During the first 100 days, close to 800,000 AIS packages were received and downloaded. 10–11 June 2013: Two new software images for the SDR AIS receiver (AIS-2) were uploaded. It took approximately 1.5 paths to upload a full AIS receiver image. The satellite showed improvement and was newly capable of sampling and decoding in real time. First metrics showed a capacity of around 6,000 AIS messages per hour on average. 25 February 2014: One year up in space. AAUSat-3 was fully functioning, and AIS measurements were done on a regular basis. A ground station was established at
Thule Thule ( grc-gre, Θούλη, Thoúlē; la, Thūlē) is the most northerly location mentioned in ancient Greek and Roman literature and cartography. Modern interpretations have included Orkney, Shetland, northern Scotland, the island of Saar ...
(
Qaanaaq Qaanaaq (), formerly known as Thule or New Thule, is the main town in the northern part of the Avannaata municipality in northwestern Greenland. It is one of the northernmost towns in the world. The inhabitants of Qaanaaq speak the local Inukt ...
),
Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland i ...
, for extended download capacity. Energy production was stable but low, so the mission was interleaved with hours or days for charging batteries. New uploaded algorithms showed reception of approximately 8,000 messages per hour and real-time performance, which meant that decoding took less time than sampling and was carried out in parallel. Due to the ground station at Thule, it was possible to carry out real-time supervision, measuring and downloading at the same time. So only a few seconds after detection, the information was available in Aalborg at the MCC. 17 September 2014: The last message was received from the satellite. 1 October 2014: The project at AAU declared the end of the AAUSat-3 mission due to battery problems (continuous decline in power production). The project is grateful for the experience gained throughout the mission.


Satellite subsystem strategy

AAUSat-3 was based on a decentralized concept with no dedicated master. The idea behind this approach was to achieve a modular satellite that, in many cases, would be able to function even when certain subsystems failed. For that reason, the must-have subsystems (EPS and COM) were designed to be simple and robust, whereas subsystems like AIS-2 were by necessity more complex, with a concomitant higher failure rate. The power system (EPS) acts as intelligent supervisor and watchdog. AAUSat-3 consists of several sub-systems: On the
ground segment A ground segment consists of all the ground-based elements of a space system used by operators and support personnel, as opposed to the space segment and user segment. The ground segment enables management of a spacecraft, and distribution of pay ...
, there were: * CDH: Command and Datahandling System * GND: Ground Station * MCC: Mission Control Center All internal and satellite-to-ground communication was carried out using CSP protocol.


Technical specifications

The technical specifications was:


See also

*
List of CubeSats The following is a list of CubeSats, nanosatellites used primarily by universities for research missions, typically in low Earth orbits. Some CubeSats became their country's first national satellite. The extensivNanosatellite and CubeSat Databas ...


References


External links


Official homepage
{{Orbital launches in 2013 Student satellites Aalborg University Spacecraft launched in 2013 CubeSats