DeepEarthScience

So, the last few weeks were quite exciting at the DopTrack satellite tracking station. We have updated the software, such that the station is now able to automatically record any satellite we tell it to record. Also, the radio antennas are installed higher in the sky for better visibility. Moreover, TUDelft students have designed software to automatically extract the carrier signal from raw recordings. And last but not least, the development of the website for the Virtual Laboratory DopTrack is started, but I will report on that later on, when we have a working website. All major steps to have our project become a real educational tool for satellite tracking.  Software update: Automated satellite tracking The DopTrack station is now able to automatically compute, when a satellite is flying over and start recording it accordingly. We just have to set a line of code in the rec.list file and DopTrack is doing the rest. An example recording list is: Delfi-C3     ...

The DopTrack satellite tracking station is in full operation these last weeks. In the Space Minor at the university during my module "Satellite Operations", students are visiting the station and record satellite signals, especially Delfi-C3 and the ISS are very popular. The students then need to determine the Time of Closest Approach (TCA) and the corresponding frequency (FCA). This requires some FFT, but I am confident that they will manage. Furthermore, our intern student has done work on the ground station. His job is to estimate the precision of the Doppler measurements of DopTrack. The last few weeks he has been working at the theory behind the Doppler measurement and some of its characteristics. So with the motto "More scientists and engineers should blog", I asked him to write a blog post about his finding. His results give a clear description about the Doppler measurement. Please follow the next link for his work: http://msondergaard.blogspot.nl/201...

The ice sheets and glaciers on our Earth are currently melting, which causes the global sea level to rise. This has of course major impacts on the 44 percent of the world’s population living in coastal areas. This melting is happening already since 24,000 years ago, during that time enormous ice sheets, up to 3-4 km thick, covered lands like Scandinavia and Canada. Scientists have done measurements of this rising sea level using the coral reefs at Barbados that show a sea level rise of 120-130 meters since the start of the de-glaciation. Imagine this for a moment; England was not an island at that time. Currently, we see a global sea-level rise of 3 mm/year, however locally the rate of sea-level change can vary significantly. For example, at the coastlines of the Netherlands we observe a 2.3 mm/yr sea-level rise, whereas the center of Sweden and Finland has a 7.8 mm/yr sea-level drop. The cause of these particular variations is that not only the sea-level changes, but also the so...

In a few blogpost ago, I showed you several figures of a satellites transmission. You know, those beautiful S-curve plots with all the colours.  Those are called spectrograms or we like to call them waterfall plots, because the radio transmissions streams up in time like a reversed waterfall. To see such a waterfall plot live in action, the University of Twente opened their antennas for you to listen and see (see link ). Yet, how to make such a figure? To start with you need a recorded radio transmission. When the website of the TUDelft tracking station is up and running you can download some data there. However, (Start NerdAlert!) you can also buy your own little USB stick that acts like a software defined radio (SDR) receiver like the Logilink DVB-T . For only 20 euros you have your own satellite tracking station. NOTE: Beware! You need the RTL2832U chip version, because a lot of open software is written for that device. It is almost plug and play, you need some software, b...

In the beginning of the 20th century the gravity field of the Earth was only measured on land. Of course, to obtain a complete image of the Earth's gravity field the oceanic area (covering 74% of the Earth) should also be inspected. However, in those days that was a difficult task. Gravity could be measured by several different instruments, but for them to work a stable platform was needed. This is difficult to arrange on a rocking ship. For example, the falling mass principle was used by Simon Stevin (1548-1620), who dropped balls of lead from the New Church in Delft, Netherlands. Later, a dutch sailor and scientist called Christiaan Huygens (1629-1695) found the relation between the period of a pendulum and gravity (I used this relation earlier in the my blog). This is now called the Christiaan's Huygens law. With it the operator was able to measure gravity with a single pendulum, but needed a stable platform, such that horizontal movement did not interfere with the...

The new lecture year is coming and the satellite communications and tracking practicum is about to start. In this lecture, students have to plan a satellite pass, record the downlink signal, and post-process this data, such that they can recover some parameters like: Time of Closest Approach (TCA), carrier frequency of the satellite, and error estimates compared to TLE (see previous blog posts: here , here , and here ). For the first part, the students need to compute when the satellite is flying overhead. There are many websites and apps that are able to give you 5 day predictions, but I wanted to see if I could do this myself. As a little boy I always had the tendency to say: 'I can do that too!'. Up until the time my father said: 'Son, you can only say "I can do that too", when you at least have done it ones.' So, living by that wisdom I want to show you how to build your own satellite-pass predictor. To validate my efforts, I am going to generate the ...

In my latest paper, GRACE gravity observations constrain Weichselian ice thickness in the Barents Sea , I use an incredible satellite data set. Starting from 2003, NASA's GRACE satellite mission is producing monthly "images" of the Earth's gravity field. These observations are so accurate that certain mass transport is visible, if you look at the differences between these "images". This new data set gives tons of information about many different natural processes. Oh and the figures are so cool! For this blog, I downloaded GRACE data (click here for information, and here for the data) from the period between 2003 and 2013, CSR release. For every spot on the Earth, I calculated the linear gravity change in this period, so not the seasonal variations. The results are shown in the figure below: GRACE gravity change during 2003 and 2013 using a 'white' noise filter of ±0.5 microGal/year. The red areas show localised gravity increase (or ma...