AAUSAT3 overview

AAUSAT3 is the third student-developed CubeSat from the Department of Electronic Systems at Aalborg University (AAU), Aalborg, Denmark. The satellite is the successor to AAUSAT-II which was launched in April 2008 and is still operational to some extent.

Identification:

• NSSDC_ID 2013-009B
• NORAD ID 39087

AAUSAT3

Project Initiation

The AAUSAT3 educational project was initiated in the fall 2007 - introducing students to all aspects of satellite design and development. The objective of the AAUSAT3 mission is to fly two different types of AIS (Automated Identifications System) receivers. One of the AIS receivers onboard AAUSAT3 is an SDR (Software Defined Radio) based AIS receiver. The other AIS receiver is a conventional hardware receiver. The goal of AAUSAT3 is to investigate the quality of ship monitoring from space.

Funding

The project is mainly funded by Aalborg University and by DaMSA (Danish Maritime Safety Administration), along with a number of sponsors.

DaMSA is particularly interested in the performance of the prototype SDR AIS receiver collecting AIS signals from ships in the vicinity of Greenland.

Balloon Test

A high altitude balloon test from Esrange, Sweden took place October 2009(Bexus09). 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).

The flight lasted 3 hours in 24 km of height and outcome was more than anticipated. Video of the ballon flight.

AAUSAT3 Design

The design of AAUSAT3 is a highly modular and distributed, with strictly defined subsystem interfaces and tasks. Compared to its predecessor AAUSAT-II, which is a monolithic system based on a centralized OBC (On-Board Computer), this presents a number of advantages, most importantly the parallel development and testing of the subsystems.

AAUSAT3 system structure

Subsystems

AAUSAT3 consists of six on-board subsystems: Electrical Power Supply (EPS), Communications (COM), Attitude Determination and Control System (ADCS), First AIS Receiver (AIS1), Second AIS Receiver (AIS2), and Flightplanner/Logging System (FP/LOG).

In a distributed system, it is a common approach to have a flight planner for controlling experiments and payloads. To have the system fail save, all subsystems must be able to operate on their own. The EPS is in charge of switching on subsystems in accordance with available power and a pre-designated plan of operations; the activated subsystems will carry out the predefined operations.

To achieve a high level of integrity of the subsystems, the following resides on their own Printed Circuit Board (PCB): EPS, COM, ADCS, AIS, and FP/LOG.

 Attach:uploads/a3ss.png | AAUSAT3 subsystems in detail

Internal Communication

Communication internal in the satelitte is provided by a Controller Area Network bus (CANBUS) using the Cubesat Space Protocol (CSP) as network-layer. CSP was originally developed for use in AAUSAT3, but is now jointly maintained by the AAUSAT3 students and involved persons from the open source community. The protocol allows subsystem to use socket-like communication between each other.

ADCS

The ADCS provides 3-axis stabilization using magnetorquers as actuators. Attitude and angular rate sensing is provided by magnetometers and gyroscopes, respectively. This is done in two seperate systems: ADCS1 and ADCS2. For further details see ADCS1 ADCS2.

EPS

The satellite is controlled by the EPS. The EPS is responsible for distribution power to each subsystem, and keeping a healthy charge on the batteries. Face-mounted solar cells are used to provide power in orbit. The power is stored on a Lithium-Ion battery (8.2 V, 2200 mAh). The supply voltage for the subsystems is 3.3 V and 5 V. EPS details

COM

The communication between the satellite and the ground station is over the UHF band with Forward Error Correction (FEC). The COM subsystem is implemented as a transparent routing device. This feature permits all subsystems to initiate their own ground communication, and it provides the ability to directly receive data from the ground. COM details

FP/LOG

The FP contains messages to the subsystems which are activated at a certain time. New messages can be uploaded during flight, and thereby allowing a reconfiguration of the FP. The FP is mainly used to setup detailed experiments in the later part of the mission.

The satellite has an overall logging system, which facilitates a common log where all subsystems can add events. FP/LOG details

AIS1

AIS1 is a hardware based AIS receiver. The receiver demodulates the radio signals from one of the two AIS channels into a 9.6 kbit/s data stream. The received AIS messages are decoded and stored on permanent storage for later analysis. AIS1 details

AIS2

AIS2 is a Software Defined Radio (SDR) specially designed for receiving AIS messages in space. The AIS2 SDR receiver has been built and tested on the ground and in a stratospheric balloon flight. AIS2 details

Launch

The launch of AAUSAT3 is a secondary payload scheduled for Q2 2012 from SDSC-SHAR (Sriharikota, India) on the PSLV-C20 launcher of ISRO. The primary payload on this flight is the SARAL minisatellite of ISRO and CNES.

Secondary payloads manifested on this flight are:

• BRITE-Austria (CanX-3b) and UniBRITE (CanX-3a), both of Austria. UniBRITE and BRiTE-Austria are part of the BRITE Constellation, short for "BRIght-star Target Explorer Constellation", a group of 6.5 kg, 20 cm x 20 cm x 20 cm nanosatellites who purpose is to photometrically measure low-level oscillations and temperature variations in the sky's 286 stars brighter than visual magnitude 3.5.
• Max Valier nanosatellite of GOB (Gewerbeoberschule Bozen), Bolzano, Italy. The nanosatellite has a mass of ~ 12 kg. The primary payload features a miniature X-ray telescope for astronomical observations.
• Sapphire (Space Surveillance Mission of Canada), a minisatellite with a mass of 150 kg.
• NEOSSat (Near-Earth Object Surveillance Satellite), a microsatellite of Canada with a mass of ~80 kg.
• AAUSAT3 (Aalborg University AAUSAT3), a student-developed nanosatellite (1U CubeSat) of AAU, Aalborg, Denmark. The project is sponsored by DaMSA (Danish Maritime Safety Organisation).

Orbit

The orbit is sun-synchronous near-circular dawn-dusk orbit, altitude of ~800 km, inclination of 98.55º, orbital period of 100.6 minutes, LTAN (Local Time on Ascending Node) = 6:00 hours.