Slowed down by vapour

Shizhuo Liu. (Photo: Tomas van Dijk)

Name: Shizhuo Liu (28)
Nationality: Chinese
Supervisor: Professor Ramon Hanssen (faculty of Aerospace Engineering)
Subject: Research on earth deformation using radar from satellites
Thesis defense: In one year and two months

“It took me several months as an MSc student to start understanding how synthetic aperture radar interferometry (Insar) works. This technique allows us to study the deformation of land surfaces by measuring the travelling time of microwaves sent from earth observation satellites. The first space-borne Insar mission operated by the European Space Agency (ESA) dates back to the early of 1990s. Before this mission, the only way to measure land deformation caused by human activities, like mining and groundwater extraction, was by ground levelling surveys, which cost considerable time, money and human resources.

I completed my BSc studies at Wuhan University, located in the middle of China, on the subject of geodesy (the scientific discipline devoted to determining the shape of the earth as precisely as possible). Six years ago I came to Delft for my MSc degree in aerospace engineering. The main reason for choosing the Netherlands is that it’s relatively cheap to do a Master’s here compared to other countries, like the United Kingdom. The fine reputation of the research conducted at the faculty is of course another important factor.
After my MSc I was offered a PhD position. The main goal of my PhD project is to mitigate the extra travelling time of microwaves caused by vapour in the atmosphere. This extra time can be very significant when the weather is cloudy and turbulent. In my research, I primarily use satellite images acquired by ESA’s ERS1/2 and Envisat satellites flying at an altitude of about 800 km and with a typical repeat orbit of 35 days. Currently, I’m working with images acquired over several years to try to filter out the atmospheric noise from the images.

From 2013 onwards, ESA will launch several new earth observation satellites to replace ESA1/2 and Envisat. One of the main advantages of the new generation satellites is the reduced repeat orbit of six days. This will allow us to filter out the noise much more quickly. And what’s more, it will also allow us to study irregular uplifts and declines in the Earth’s surface, which happen over short time spans, such as, for instance, during earthquakes. When you only receive images every 35 days, it’s sometimes difficult to say what has actually happened during that time span.

I like my project very much and am having lots of fun working with computer models. I like the logical way of thinking that I must adopt. I also think it will be useful to me in everything I do in life.