UNITEC-1 Tracking Report

I’m sorry to report that despite coordinated efforts between Japanese and European teams we have not been able to receive any signal from UNITEC-1 over Europe. Japanese ground stations were able to receive both the orbit determination downlink and the major/minor data downlink during the first pass after launch; however, the signal has been lost during the first mission day sometime between LOS over Japan and AOS over Europe.

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5.8 GHz Helical Feed for the 90cm dish

Yesterday was day 2 where we were repairing the broken Azimuth rotator and making a small 90cm dish ready to track UNITEC-1 on 5.84 GHz. Actually, we already fixed the rotator on Monday but we ended up mounting it 180° off and we decided to fix it properly instead of just correcting it in software.

Fixing the orientation of the Azimuth rotoator was very quick – it took only 17 minutes to get up to the mast, lift the antenna construction, change the orientation of the rotator and fasten the nuts and bolts again. We had the practice from yesterday.

Next item on the agenda was to make a small helix with two turns to feed the 90cm dish so that we can use this smaller dish for tracking UNITEC-1 in the beginning of the interplanetary cruise. We found some online helical antenna calculator to generate the design but that was more than 1 GHz off and it took a lot of tweaking and tuning to get it close to 5.8 GHz. Here are the results, photos and videos.

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Smaller dish for tracking UNITEC-1

As you probably already know the UNITEC-1 launch got scrubbed today (17th May). Fortunately, there is a launch window every day for the next few weeks.

During the last few days I learned that tracking UNITEC-1 will be very difficult because the available trajectory data can be very uncertain. Therefore, we decided to use a smaller antenna with wider beam width in the first few days after launch. One option was to mount the IKEA dish to piggyback the 7m dish, another option was to use a 90cm dish which is currently equipped with a 2.4 GHz feed. We decided to go for the second option.

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Preparing the 7m antenna for UNITEC-1

AMSAT OZ staff are preparing the 7 meter dish for tracking the UNITEC-1 interplanetary spacecraft.

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Gpredict on the Eee PC 701

Now that I have Ubuntu 9.04 runnign on my Asus Eee PC 701 it was very easy to get Gpredict up and running. After a few configuration tweaks related to the views it runs and looks very well even on this small 800×480 pixel display!

Watch in high resolution.

Thus, I have now following hamradio applications running on the Eee PC:

Gpredict 1.0 beta 5 released

Ten days after the release of Gpredict 1.0 beta 4 we are now ready with a new release that fixes some minor bugs in the radio controller.

The significant changes in this release:

  • Fixed some bugs that caused the Doppler shift to be calculated incorrectly in some cases.
  • Fixed a bug that could cause the transponder frequency to “drift” away from the set frequencies.
  • Added new transponder files received from David VK5DG.
  • Minor enhancements in the user manual.

You can download the source code from the project page on SourceForge. Try it, test it, discuss it, and report the bugs you encounter!

 

Gpredict 1.0 beta 2 released

Finally, the Gpredict 1.0 beta 2 release has come together, featuring a completely rewritten radio controller / Doppler tuning algorithm. It became a bit more complicated than I originally anticipated, because the incoming requests for improvement of the original controller did not limit themselves to controlling the downlink and the uplink, but also called for using two different radios.

Given that there are very few full-duplex radios out there designed for satellite communications and that they are very expensive, I found this request to be very reasonable and decided to implement it. The resulting controller should be able to work using receivers, transmitters, half-duplex transceivers, and combination of those. Full-duplex has not been implemented, because I am not sure whether hamlib is able to do that properly. That will be implemented in one of the upcoming betas.

The new radio controller
The new radio control UI. See more screenshots.

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Gpredict Updates

I just realized that the last time I have blogged about my pet project, Gpredict, was back in February 2007. Back then, the big news was the Sky at a Glance function and there has in fact been a lot of evolution since then despite the big silence in the Gpredict Developer Blog. Let me try to sum up the progress from last two years as well as what you can expect to happen in the weeks to come.

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