When you read about LISA Pathfinder and space Fundamental Physics missions in general, you likely encounter the term “drag-free”. One of such missions is Gravity Probe B a Stanford University led mission primarily devoted to study one of the effects predicted by General Relativity, the Lense-Thirring effect or so-called frame dragging, launched in April 2004. Another drag-free mission is the ESA GOCE mission devoted to the measurement of the Earth global and local gravity field and geoid launched in March 2009. The very first drag-free mission was an American spacecraft called DISCOS developed in the late 60’s under the leadership of the father of “drag-free” Prof. Dan DeBra and launched in 1972. But what is drag-free really??

What has to do the weight of a fog-droplet with astronomy? Well, to detect gravitational waves you have to shield the detectors from all disturbances to the level of the weight of a fog-droplet ( few nanograms) or a medium size bacterium.

In my previous post I explained what gravitational waves are and how important they are (or may become) for the observational astronomy. Before we can proceed and explain what we do in practice to achieve this formidable goal, I need to tell you in short how you can detect gravitational waves.

Here I am with my first post! It’s the the first day of 2009, the year of Astronomy! As you see in the side bar, I am not actually an astronomer. So let me explain you what I’m doing here