Hubble Servicing Mission 4 Blog

Head of ESA Solar Generator Section Lothar Gerlach stands in front of the countdown clock at Kennedy Space Center just before the launch of Atlantis for SM4.

Name: Lothar Gerlach

Title: Head of ESA Solar Generator Section

What is your area of expertise?

I have more than 30 years of experience with solar cells and solar generators.

What made you choose this field?

I wanted to go to northern Germany and I opened a newspaper and found a job. I first worked for a company manufacturing solar generators for ESA. My first project was Spot 1, a French Earth-observing satellite. I designed the electrical network for the solar generator.

Tell us about the challenges of designing the power source for a spacecraft.

A solar generator is exposed. It is, in principle, the subsystem with the most interactions with different spacecraft subsystems and the harsh space environment. We have to survive the launch, we have to generate the power and we are outside. All of our equipment is exposed to radiation, thermal cycling in extreme case up to 230C and down to around -200C and other space hazards (such as debris and micrometeorites). We have to design our solar arrays to be compatible with other subsystems such as the ACS (Attitude Control System) because uncontrolled ACS movement could damage the solar generator.

In general, we also have to permanently improve solar cell efficiencies to reduce cost and weight. The cells constitute about 40% to the overall solar generator cost. Also, the larger the array, the more fuel is required to control the attitude of the satellite. Depending on the mission, we go to extremes - close to the Sun or to deep space. We can design solar generators for going to the Jovian system, but not beyond (because the Sun’s intensity is too low at that distance).

How have Hubble’s solar arrays and the drive mechanisms and electronics performed?

So far, everything is going like clockwork - nothing unforeseen has happened.  And we are very happy about it.

How do you feel about supporting what many call the most powerful astronomical tool of our time?

For me, HST was always very emotional because I was involved since the beginning of development. In 1993 and 2002, the dream of every engineer came true for me: I got my hardware back from space and got to inspect it.
This mission brings back memories because you meet up with your old colleagues who were old to begin with 20 years ago; they haven’t aged, but I have.  I went from red hair to gray.

Do you have a favourite HST image?

Ultra Deep Field - I’ve used it in my photo collages. Hubble has served as inspiration for me in my art as well. I have created a mosaic of Hubble using solar cells.

Lothar Gerlach made this Hubble mosaic out of solar cells and Kapton tape. The crew of Servicing Mission 1 (STS-61) signed the artwork.

Have you worked all of the Hubble Servicing Missions?

Yes!

What has been the most exciting part of SM4 for you so far?

Launch and Hubble approach. Seeing the old baby - the grown-up baby - back!

What has been the most stressful part of SM4 for you so far?

Lack of sleep

What is next for you?

More work on solar cells. We are currently collaborating with industry partners to design an array for the Solar Orbiter spacecraft that will get as close as 0.22 AU; that’s about one-fifth of Earth’s distance from the Sun.