During this week much time has been spent on the computer trying to calculate some theoretical values for the infrared absorption part with MATLAB. Like at which altitudes the measuremnts optimally should take place or the maximum distance between the FFUs before the signal to noise ratio gets too big. When you spend much time with MATLAB and digging deeper and deeper into the infinite depths of precious useful functions one stumbles upon the knowledge that MATLAB has not only one but several ways of calculating the pressure and temperature at different altitudes. The joy is almost indescribable. Amazing!
Soon the calculations are finished and the ordered infrared sensors arrive which means that we can begin testing. We are looking forward to that!
ISAAC's main, technical objective is to design, build and demonstrate the function of two free-falling units with one of them always tracking the other. A light source on the ‘target’ unit will allow the ‘tracker’ unit to find the target. Both units will be spin-stabilized and the tracker will have a despun part with a mechanically actuated mirror to allow a two degree-of-freedom control.
So what are the two degrees of freedom? The two degrees of freedom are look angle and azimuth angle, perspectively, as showed in the below figure. The look angle is the angle between the disk plane and the direction to Tx from Rx to Tx in Rx body frame, and the azimuth angle is the angle between the projection of the direction to Tx onto the b1b2 plane in the Rx body frame and the b1 axis of the Rx.
For now, we have derived the expression of the two angles, and simulated them. The result is illustrated below.
The reason for them are kind of complex. Due to the lateral angular rates, there is wobbling. There is a visual presentation on the website http://www.ifmo.ru/butikov/Applets/Precession.html. More analysis on the reason is proceeded.
I write this post today not from the confines from my room in Stockholm but from a hostel room overlooking the mountains ranges of Abisko national park. A weekend hunting for the so far elusive Aurora and a retreat from REXUS =) =P. This week was a really busy week for the optics team. We began searching for parts of the optical system that will be used in the experimental and tracking components of the Free Falling Unit (FFU) Rx. In order to complete spectroscopy one FFU (ISAAC Rx) must track and record the IR light emitted from the other FFU (ISAAC-Tx).
The optical system under design will capture the light emitted from the ISAAC-Tx and split it. The optical light will be directed to a camera for the tracking of the Tx and the IR radiation sent to the detectors to complete the experimental objectives of the ISAAC mission.
Speak to you soon! =) Happy hunting,
During this week we have started playing with an FPGA, reading and looking at the heritage designs and learning how to use the software tools. It was a desperation the first day in which nothing worked, even the most trivial things!
However, finally LEDs started to blink! signals started to go out and everything started to work as expected. The FPGA started to live! But now a lot of work is waiting for us. Making some LEDs blink is funny, but we need to go deeper, we need to control our systems with the FPAs. Scheduling the communications, analysing the measurements of the sensors, generating the signals to control the different subsystems, storing data into the memories…
A lot of work is needed but just looking at the LEDs or the signals in the oscilloscope encourage us for keep working on it. At least until after several days trying to do something nothing works as expected, but at the end, it will work!
This very professional-looking setup was used by Emil (who later turned into a blonde popsicle out in the freezing Swedish Cold) to measure how far away it is possible to capture camera images of our LED. This will tell us a lot about the distance between the FFUs which will be optimal for good tracking. And we must say we were very impressed with the preliminary results! One single LED was visible from 1300 meters away.
This week we are working very hard with designing the PCBs that are going to manage the tracking. It’s a time-consuming process, but we’re confident that we’ll produce something cool.
Here we are, one week after the PDR still trying to assimilate everything that happened during the one week in Germany. A handful of specific oriented meetings as well as general meetings with all our the team members and supervisors helped bring everyone up to speed on what has been done and what needs to follow. But since we never got a proper chance to celebrate our “conditional pass” we figured the best way to keep our motivation up, as well as ease our struggle to meet the new deadline, is to have a “fest med ISAAC”.
Since Emil has a free apartment at hand, which is also conveniently located in one of the most renowned student neighbourhoods in Stockholm, we decided to make it ISAAC’s relaxation headquarters for the coming evening. Everyone was invited and hopefully will show up, turning a rather cold and lonely Friday evening into a snug and enjoyable, off the record, meeting with as few FFU design discussions as possible :))
Have a great weekend and keep close, embarrassing pictures are coming!
Oh, I almost forgot, keep your eyes out for asteroid DA14 tonight which is due to fly past Earth in a few hours (19:00 GMT to be precise). Who knows, maybe we’ll turn this celebratory get together into an “End of the World” party.
Also, for those of you who do not own their own astronomical observatories (or do not have the possibility to go to an observatory tonight) here’s a live stream from NASA covering the event as it happens: Asteroid AD14 live coverage.
Just today we received the report from the experts about our PDR. And we have passed with conditions. That means that there are a few issues that need to be addressed in the next version of the SED (student experiment documentation), which is due on 11th March, and when the expert panel is happy with our modifications we may go on with the project.
The required modifications concern mainly our RMU (rocket mounted unit). As you can imagine, if you cut two big holes in a rocket it will influence its ability to cope with the loads during launch. The acceleration reaches up to 20 g, which is much more than a human would survive. To make sure that the rocket doesn’t break apart we need some reinforcement to compensate for the holes. In the REXUS programme, as usual in the aerospace industry, safety comes first, therefore the expert panel requests a very detailed analysis of the RMU and its reinforcement.
But of course we’re also working on the other parts of the experiment. The CAD design of the FFUs is one thing we focus very much on these days. You’ll probably hear more about that in another blog post soon. And the electrical engineers are busy selecting components and drawing schematics.
And by the way, the MUSCAT team is also very busy with the last preparations for the delivery of their experiment. When we look at their experiment and compare with the state of our design (MUSCAT was at that point one year ago), we are impressed by what a group of students can achieve in a year of work. Let’s hope that all goes well for their delivery and the flight in May, and let’s keep working on our experiment to get there as well next year.
For more about MUSCAT check out their website: www.muscatexperiment.se