AAUSAT-II One year birthday April 28th

AAUSAT-II will be one year old on April 28th and it is time to move from home.

After one years with nursing, learning AAUSAT-II to roll and ending up with the ability to walk by itself, AAUSAT-II is now capable to be on its own out in the world.

When your child leave home your daily contact and nursing will change to more sporadic contact. This counts also for AAUSAT-II. We will from time to change checkup on what AAUSAT-II is doing and still help by demanding som detumbling from time to time.

It has been a great year and we thanks many times for the help from all around the world in the process of breeding AAUSAT-II. Without your help the story could had ended in another way.

Without help from our sponsors no AAUSAT-II in orbit. So many thanks for your help.

We do also appreciate all the attention from the medias and we hope that people around had some fun following our breed of AAUSAT-II with all the ups and downs.

On Tuesday April 28th we will celebrate it in satlab at 11:30 (UTC+2). Erverybody are welcome to join us for a cold drink when we will say hello "and see you sometime" at 11:41 when there will be a pass.

Here's a little movie with some of the memories from 2007 when AAUSAT-II was moved to Canada to be in transit until launch.

Wednesday March 11th 2009 - WE ARE BACK !!! danish vrs

We have this evening upload a small new SW image onboard AAUSAT-II!!!.

On February 10th did we loose our flash or rather is was corrupted, which had the impact that newly uploaded SW was lost and that operation was degraded due to lack of storage.

Since then we have being thinking, planning, testing etc etc so we could be sure that an operation would be a success.

After (another) review of onbard flight SW - (mostly around reboot, flash etc) it was decided to make a small image for upload. If it could be uploaded it will be a test of correctly working flash.


So - AAUSAT-II is now back in business !!!

This is extremely good news because we have being afraid of loss of our flash - which had a very negative impact on the mission.

The image is very small so we have not tested all bits and bytes in the flash. This may very well be the next step.

Boot table shows new image in bank no 7.

As you can see a new small image is in bank no 7.

Overview over AAUSAT-II. Notice confirmed upload!!

Why this temporary loss of flash ?

  1. Reboot when writing in flash
  2. Radiation
  3. ...

We will the coming days update our homepage when we have more new news :-)

AAUSAT-II last seen ...

Christmas Evening December 24th dansk version

has AAUSAT-II being around

in orbit for 24 * 10 days :-)

AAUSAT-II is now the second longest living Danish Satellite in Orbit. (No. 1 is Ørsted)

We have had a fantastic campaign after the launch April 28th.

The mission has been a greater success than our wildest dreams!

We are looking forward to 2009. There are still things we would like to do with AAUSAT-II.

You all know - it is our baby :-)




If anybody likes what we have doing then

we have already started on the next satellite AAUSAT3

As many other projects we do rely on sponsors and we will ofcourse be happy if somebody wants to help us.

More info can be downloaded here(pdf)

Friday November 28th - dansk version

Last news Friday evening 9:14 PM GMT+1

We had a very good pass despite non optimal weather condition

  • First contact with 5 degrees elevation. AAUSAT-II was around Cairo - Egypt
  • Detumling was confirmed activated at 13 degress elevation - south of Rome
  • Got log data down at 26 degrees elevation around the Alps

Indeed not so bad ...

We can on our logdata see that detumbling is working.

We hope that we within a week or so can continue upload of new SW.

earlier today Friday

We have now got our 1100 W amplifier back from reparation :-)

We have now installed it and testet the amplifier - it works !

At the first pass today we got contact imitatively !!! and got logs etc down and restarted detumbling.

So we are back in business :-)

We will now continue with our plans:

  1. Getting tumbling under control again
  2. Continue upload of new SW image

The new SW we are uploading has increased autonomy so detumbling will be carried out without interference from ground, so we can continue with our mission :-)

Stay tuned

Saturday November 15th - dansk version


Yesterday we did pass 200 days in orbit !!! and no observable degradation of AAUSAT-II.


On http://www.control.aau.dk/~kresten/stuff/s_meter_logs/tumbling_freq_over_time.png you can see we are still able to keep tumbling at an acceptable low level.

For some weeks ago we ran into a hardware fail on our 1 kW sender and are awaiting its return from reparation.

When we are waiting we are using our ICOM 910H for contact and have only abot 40 W for uplink. This had the implication that SW upload of new image has been temporarily suspended due to to many uplink errors and we are using passes for activation detumbling only.

However a substantial part of the new image is already up in AAUSAT-II so we are convinced we will succeed.

SO WE ARE HAPPY - IT IS ALIVE - and we see no observable degradation.

From the beginning a half year operations was our wildest guess - we have now passed that milestone !!!

We can also observe that autumn and winter in Denmark gives a degraded linkbudget as anticipated.

We hope to get our 1 kW blaster back next week so we can continue SW upload :-)

Wednesday October 1st - danish vrs


In the first trials we did succeed in uploading an modest amount of data to AAUSAT-II and store it in flash. The experiment was solely carried out from Schweitz. (Kresten is pt there)

This indicates that we hopefully will be able to upload new SW to AAUSAT-II.

We will spend the coming weeks on preparation of upload of new SW images for our main computer.

Among other things we will do a work around so we hopefully can prevent the rebooting all the times - this will lift our operations to a new level :-)

Tuesday September 30.

During the last five days we have not being able to send commands to AAUSAT-II - and therefore has detumbling not been active as you can see on the picture below. In the end it showed up to be a damaged cable between our modem and radio. So we are back in business, and are preparing SW upload in the comming weeks if everything goes ok.

Tumbling frequency over time

At the picture it is clear that an active force on AAUSAT-II accelerate the tumbling when no detumbling is active. So we can now conclude that the high rotation was not only a result of the launch end ejection from the rocket. AS a result we must be detumbling AAUSAT-II the rest of its life to be able to have a descent communication link.

Sunday September 14th - danish vrs

The last week we have continued spinning down AAUSAT-II.

It seems to work pretty well :-)

Tumbling over the last +100 days (Sep 13th)

The blue line is the rotation frequency - as you can see we are now down at a rotationfrequency around 0.2 Hz. As AAUSAT-II is rebooting approx 11 times every 24 hours are automated groundstation do setup B-DOT detumbling in every pass.

The red curve is twice teh frequency as the blue one due to two blind spots on every rotation - so the radio signal fades two times on every rotation,

Radio signal from Sep. 13th 09:45

Sunday September 7th - danish vrs

Without HAM people no student satellites!

Our hampage mention some of the active HAM radio amateurs helping us.

Friday September 5th - YES our detumbling is just workingDanish version

Comming from close to 1.5 Hz our tumbling frequency is now in the area of 0.45Hz We have also observed that downlink package loss has gone from more than 90% to abour 40% - which is acceptable.

At the evening pass (Sep 5th) we had a packet loss of 25% in the middle of the pass :-)

10Hz s-meter log og analyse for 21:52 pass sep 5.

The evening pass was conducted by a crew member temporary in Texas and one in Aalborg. Finally a evidence for that the internet can be used to something ;-)

We have the first version of our SW ready for upload when we get the tumbling more down in the near future.

Monday September 1st- Continued Success :-)

AAUSAT_II has been in space for 126 days - more than three months.

After AAUSAT-II during a timespan of 40 days have been spun up to a rotation fare of 1.5 rounds per second (RPS) our anti spin system (detumbling) is regaining control of the satellite.

As can be seen from the plot below the detumbling algorithm works i.e. the B-Dot algorithm works as intended by reducing the rotation rate of the satellite. As of August 31st the rotation is estimated at 0.5 RPS and we expect to be able to decrease it to near 0.

Tumbling frequency over time

We are still working on finding the reason for the fast rotation rate, especially why it accelerated over the course of 40 days. We have a number of ideas, which include the torque caused by the magnetic dipole generated by the solar cells.

We are still experiencing regular and unintended reboots of the main computer, but at a smaller frequency. Each reboot causes the detumbling algorithm to be deactivated and we then reactivate it on the next pass over Aalborg. We therefore estimate that the detumbling controller is only active 4-8 hours per day and considering the very fast rotation rate of AAUSAT-II, we are very satisfied with the performance of the controller until now.

With the current state of affairs we are hoping to resume normal operations of AAUSAT-II in the near future. One possibility is to upgrade the main computer software to remove a few bugs and prove that we can :). More details to come.

The frequency analysis from a good 83 degree pass the 31st of August 12:56 shows that the rotation frequency has been brought down from 1.5 Hz to apr. 0.6Hz. This has caused the packet error rate to drop from 90% to around 40%.

DE-TUMBLING 28th of August

Seeing that shorting-circuiting the coils had some effect on the tumbling-rate of the satellite, but not enough, we have turned on the de-tumbling controller even though it was not designed for such high tumbling-rates. The plot below shows the estimated tumbling frequency over time based on the received signal strength (RSS) measured on the ground station radio. The reason for basing our estimates on the radio signal and not the on-board sensors is that the high tumbling rate makes reliable communication difficult.

However with our new 1KW PA we have no problem sending commands to the satellite so we request housekeeping logs to be transmitted and measure the variation in signal strength. RSS varies as the satellite rotates because the radiation characteristics of the antenna is not uniform. Thus the power transmitted is greater in some direction than others and this yields a varying RSS at the ground station.

Two dominant frequency components are found using the frequency analysis of the signal as shown below. The frequency plot for today can be found here

Tumbling frequency over time

We have run the de-tumbling controller from day 112 to 115 with the nominal, but low gains, and from day 119 with a higher gain. The result is that tumbling rate decreases significantly faster in the second period as can be seen from the plot. We can therefore conclude that the de-tumbling controller works and we expect to be able to resume normal experiments.

Detailed plots are available here:

Wednesday August 6th - 100 DAYS HAS PASSED SINCE LAUNCH

(Launch was April 28th 05:53 AM DK summertime) 100 days has passed since our successful launch from India on a PSLV.


  • AAUSAT-II is still in operation and we are in daily contact
  • Full energy production on-board as on day 1
  • Still "regular" reboot of main computer with intervals of 1-4 hours
  • We have not being able to get decent science data down from our radiation detector payload from DTU Space
  • ADCS sensor part has been activated and data received for further investigation.
  • Our ground station is running perfect and autonomous (fully automated)
  • We have our own 1 kW sender (Beko 1100) and many thanks to Verner for his help with our borrow of his private and home made 1 kW Sender.


Today it is 44 days since we started tumbling investigation. In that period the tumbling rate has gone from 24 RMP to more than 60 RPM. We are not sure why and will for the time being not make guesses.

We can't confirm that the ADCS system has and/or are on for periods of time.

Until now we have collected data - like S meter measurements from GND - but now we have a packet loss of more than 80% due to the high tumbling rate.

So ...

We have now started an alternative de-tumbling based on short circuiting the magnetorquer coils.

We will let it run for 2 weeks and follow up on the results.

As AAUSAT-II regularly reboots we have are autonomous ground station to switch on this de-tumbling for every pass over Aalborg.

As we are not sure about "why" we will wait with an explanation of this phenomena.

Old news can be found in our News Archive

TUMBLING (8/7 kl 11:02)(Danish version)

We do still have som tumbling. Mike Rupprecht DK3WN (Germany) reports an estimated tumbling rate of 24 RPM!!!!

We can see that the tumbling started the night between 6/7 and 7/7. The same night at 2:15 we did pass IMS-1 which is a 80 kg satellite on the same launch as ours.

ADCS has not been switched on, and due to the design with several computers involved in ADCS we do not believe that is has been switched on by itself.

On the other side - satellite collision is not daily business ...

lets us just say: we are thinking, wondering and analysing the situation.

The high tumbling rate does not ease communication.

We are working on the case.

The mission continues (July 7th)

AAUSAT_II is still i operation. We have up times up to 11 hours ! We have still not being able to get descent data down from radiation payload.

There may be more than one explanation on that:

  • Lack of time (examines and summer holiday ;-)
  • We are only sending with 400 WQ. WE are waiting on a 1000 W amplifier from Beko, Germany
  • Rotation/tumbling frequency seems to have gone up ???? acc to beacons

Except from that ussual business: lots of power on board, descent uptimes.

So we continues operation


Today at 11:30 the radiation detector based on a crystall from DTU Space was turned on from ground.

It responded positive and in the following minutes science data was requestet and downloaded two times.


We will follow up tonight where we have two good passes. The first will be used for turning payload on and the next 90 minutes will be used for downloading science data.

We will come back with more news :-)


A large log was requestet downloaded during the pass

#0 sek log data"

As you can see it "just came down"

AAUSAT-II did transmit continuert for 30 seconds

Natinal TV2 NORD was present in the radio room and the whole seance was in the news the same evening ( a 1min 57 sec lon report :-)

As you can see AAUSAT-II is thumbling.

We are very happy for this recording an will analyse it in the comming days.

ONCE AGAIN CONTACT!!! (June 20. 22:30)

At the pass at 2200 we did try to communicate with AAUSAT-II again.

And as at 20:27 pass there was full contact !!! We did have 6 verified communications.

Verner (OZ5TG) aside his 1kW/10dB PA rack we have borrowed

So the mission has once again taken a leap forward. We are now the proudly owners of a spacecraft in operation and control.

Only six hours after Verners 1kW/10dB amplifier was in operation we were in full contact - what a day :-)


After we have started using Verners (OZ5TG) +400 Watt amplifier somthing has started to happen

At the first pass after the +400W uplink was i operation we had a 20 degree pass at 20:27.

We did send a number of TimeSync packages and ...



So once agin - Many thanks to Verner (OZ7TG)

Our first real communication with AAUSAT-II

From our MCC:

20:33:02 Timesync ack 1:
+++++++++++ Checksum match, 
raw length; 8, 
Callsign: OZ2CUB
MCC_INTERFACE: Sending command to MCC ->
c0 00 02 80 d1 f7 5b 48 
 08 0e 00 7c d6 58 48 01   ......[H ...|.XH.
02 c0                                              ..
Received: 41, Checksum ok: 13, PER: 0.683
Last uplinked packet rssi: -95.4, hferr: -2.2

20:34:35 Timesync ack 2:
+++++++++++ Checksum match, 
w length; 8, 
Callsign: OZ2CUB
MCC_INTERFACE: Sending command to MCC ->
c0 00 02 80 2e f8 5b 48  
08 0e 00 a4 ff ff ff ab   ......[H ........
fe c0                                              ..
Received: 45, Checksum ok: 14, PER: 0.689
Last uplinked packet rssi: -93.3, hferr: -2.6


Yesterday we got a call from Verner Topsøe(OZ5TG) with an offer to borrow his 1kW/10dB UHF PA stage.

Verner had followed our mission in the Danish Engineering Society homepage and more important seen a "PA wanted on Experimenting Danish Radio amateur(EDR)'s homepage.

To make it short - we did say Yes - and THANKS!!!

Verner is a member of Esperimenterende Danske Radioamatører(EDR) which is the danish Society for Radio Amateurs. We can only give them our warmest recommendation !!!

It is "just" a Society of nice and very helpfull people !

On the picture is Verner aside his PA rack - very impressive.

It gives 400-500W (10dB on top of our ICOM 910's 40-50 W)

And Yes - the amplifier is Verners own construction :-) I believe it is based on a GS35B triode

So today Verner came the way from Horsens (160km) together with his wife and spend the whole Friday helping us getting his beast up and running. So we did solder, setup relais etc etc. It is not "just" when you are going to let up to 1kW enter your antenna system - but we did succed :-)

It is so nice to meet such helpful and nice people :-)

So everythign is now running - and we are waiting on a high pass later this evening at approx 2200 UTC+2

We did had a try in the end of a low pass and AAUSAT-II could hear us and with higher RSSI than normal - so ... we are waiting now :-)


On Saturday June 7. at 11:27 we had success in sending a command to AAUSAT-II and as yesterday indirectly confirmation from AAUSAT-II by beacon "reply"

So we are on the right track !!!

Mike DK3WN (Germany) has confirmed and received the same beacon today !!!

So two groundstations has now received same beacon with up link information

Thanks a lot for his effort in helping us !!!

FINALLY - WE GOT IT !!! (June 6.)

During a pass on Friday June 6. we did try to establish contact from ground to AAUSAT-II.

Shoot followed by first beacon which confirms hole through!! '

No immediate answer - but ...

In the following beacons we could see:

  • AAUSAT-II had received a packet from ground
  • the packet had a checksum error :-(
  • Up link call sign (OZ2CUB) was inserted in the following beacons
  • and radio signal strength(RSSI) and frequency deviation was inserted in the following beacons

So - AAUSAT-II did receive our call and did try to understand us !!!

and - of course - reported this back in the following beacons

So we are still very very very happy

On the same day we did announce stable down link we got confirmed communication from ground to AAUSAT-II !!!

Because this is an indication on that we are now hopefully in a good position to establish real two way contact to AAUSAT-II.

CDH viewer with first beacon with proof on hole through '

So we have today received much valuable information that makes us beleive that we can reach our final top top goal : communication with AAUSAT-II.

It seems that we have to go through a similar procedure as we did with our down link(like stronger radio)

So we will continue working :-))))

Uplink is next ! (June 6.)(Danish version)

Downlink is now considered as stable as possible. So the next will be getting uplink in operation.

Command Center after beacons from 69 deg pass June 5. 22:11'

During the last days we have being shooting at AAUSAT-II but from next week we will start ca systematic scanning for finding the right uplink frequency. AAUSAT-II downlink is 7kHz above the nominal frequency so we may see similar deviation on uplink frequyency.

Parts of series of beacons on 69 deg pass June 5. 22:11'

AAUSAT-II's reciver is quit narrow so we will over the next week or two do a systematic autonomous sweep on uplink frequencies starting from - 10 kHz to +10kHz. We will only do it on good passes (more than 35 degr elevation)

This will take days or even weeks, but as AAUSAT-IIs is quite stable we do for the time being see no near end of operations.

Old news can be found in our News Archive