End of OperationsAfter having listened for DTUsat using several different ground stations over the last 6 months, we are forced to conclude that DTUsat did not work in orbit. Since we have had no contact to the satellite and thus no debugging information, and since both flight- and flight spare performed flawlessly in our tests, we cannot say what went wrong. Even though the satellite did not fulfill its mission, the main goals of the project are still achieved: Education of 70+ students, a lot of outreach activities and a satellite, which was declared flightworthy. Unfortunately and sadly, the rest of our goals were not achieved, but the DTUsat project is still an achievement to be proud of.
Members of the project met on March 26th 2006 and celebrated the 1000 days anniversary of DTUsat. The flight spare hardware still works, but the modem CPU has evaporated and found other things to do in life. We also debugged the script generating the banner, making it work with 4-character numbers.
The ProjectDTUsat is a picosatellite designed and built by students from the Technical University of Denmark, DTU.
The main payload of DTUsat is an electrodynamic tether for dumping the satellite. The tether is deployed using a novel yo-yo system, greatly simplifying construction and deployment. A calibrated test transmitter is flown as secondary payload. The satellite is 3-axis stabilized using magnetorquers, while attitude determination is done by a combination of a 3-axis magnetometer and 5 chip scale dual-axis sun angle sensors designed and built for this satellite. The mass of each sun angle sensor including supporting electronics is only 3 g. All flight electronics is designed using modern 3.3V CMOS integrated circuits, lowering total power consumption to about 400 mW while providing about 10 MIPS for application software.
All electronics in DTUsat is commercial 3.3V small-geometry CMOS to conserve power. We have tested for Total Ionizing Dose, which caused a maximum of 50% power consumption increase over the projected radiation dose. This is well within the power envelope of the system. The first chips are tested to fail at a total ionizing dose of about 7 krad, which translates to about a year given our shielding and orbit. This is sufficient for the mission. We do not yet know the rate of Single Event Upsets, but we have designed a global protection system, that shuts down and reboots the entire satellite by turning off the power supply if a latch-up is detected. Latch-up detection is decentralized to local sensors. Due to lack of power, weight, and time, we have opted for a simple configuration with little redundancy.
DTUsat will share the honour of being the first CubeSats launched with the Danish AAUsat, the Canadian CanX, the American Quakesat, and the Japanese XI-IV and Cute satellites. The CubeSat concept originates from prof. Bob Twiggs of Stanford University.
In commercial satellites, the reason for launching a satellite is the payload. The rest of the satellite, the platform, is built solely to provide the payload with necessary services such as power, communications, etc., but serve no purpose for the satellite mission. A university satellite like DTUsat has a less straight-forward division. Although it is easy to point out our main payloads, the platform is at least as important. The reason for this is that the most important "payload" is not even launched, but remains safely on the ground. It consists of the experience and knowledge we gain by designing and constructing the satellite. Apart from educating engineers, we see a great potential for public relations in DTUsat, for science in general and DTU in particular. DTUsat presents a possibility to counter some of the prejudices that exist on engineers and scientists. We believe that these prejudices are based on an assumption that the work is boring and repetitive, while we experience a very creative, dynamic and enjoyable process. This project provides a lever for communicating that view. The purpose of DTUsat is thus threefold - scientific, educational and long term public relations.
In order to structure and evaluate the success of the project, we have set 10 success criteria for DTUsat.
A total of more than 70 students have been involved in designing and building DTUsat. For some, the project has been a single course and a two-week project. For others, DTUsat has filled a (more than) fair share of their studies for two years. All have learned a lot - not all of it technical, as running a project as large as this presents a very different kind of challenges on top of the technical and interface-related. The project has involved, at some point or another, most sections of the Technical University of Denmark. Apart from support from most parts of the university, we have enjoyed a lot of help from companies in the field. Neither the total budget of about $200,000, nor the technical difficulties we encountered during the project, would have been possible to shoulder without our sponsors
Please feel free to contact us or to look around the site for more details on DTUsat.