Hundreds of people who entered my office for the first time over the past 10 to 12 years, wondered what the big black and red 1 by 1 m massive looking “engine block” was, protected under a Plexiglas cover. Proudly I explained them it was an important heritage of my former life in space industries. It was the Breadboard model of the Optical Bench of the SCIAMACHY instrument, a highly advanced atmospheric sensor that had flown on ENVISAT and that was developed by a joint team of space industries and institutes from the Netherlands in the nineties. I had been a leading member in that team.
Donation to the National Space Museum
Last Friday February 7th I donated the full-scale authentic model to the National Space Museum in Lelystad, the Netherlands. The museum will be the location for the third stage of its life, after its prime use as a breadboard to practice the optical alignment and later as a demonstrator in my master course Space Instrumentation Engineering. By the donation to the museum, this heritage and master piece of Dutch space instrumentation engineering will be preserved. It will be made part of the exposition in the museum.
Why the model ended up in my office
Between 1993 – 2000 I had been the Systems Engineering Manager for the design, development and verification of the state-of-the-art space borne Earth observation instrument SCIAMACHY and its test equipment. Working in a highly interdisciplinary and international team of highly skilled technicians and test engineers, experts in optical and detector engineering, mechanical and thermal engineering, operations engineers, data scientists, atmospheric scientists, agencies and managers.
After the completion of this project I got a position at the Faculty of Aerospace Engineering of Delft University of Technology, where I instigated a course in Space Instrumentation Engineering in 2006. When TNO-TPD cleaned up their lab spaces about 13 years ago, in need for floor space for new projects, they asked me if I was interested in having the breadboard model. Thus I became the owner of the more than 120 kg weighing model. It ended up in my office. My upcoming retirement next summer enforces me to clean up my office and make floor space available for my successor.
The Breadboard Model 2&8
For the joint industrial SCIAMACHY team of engineers and specialists from Dutch Space (Leiden), TNO-TPD (Delft) and SRON (Utrecht), the development of such advanced new-generation sensor was a challenge. Especially the complexity of the optical train that collects and splits the incoming light in eight separate optical channels, in combination with newly developed state-of-the-art detectors that had to be cooled to cryogenic temperatures, was phenomenal.
Early in the C/D phase we decided to build a breadboard model to practice the integration and testing, and prove to be able to align all optical elements and its detectors to the very high accuracies. By subjecting the model to the operational space conditions, we wanted to get confidence in the predicted shift of spectral lines over the detector pixels, once the optics and detectors, mounted at room temperature, would cool down to -20 and -125 degrees C respectively.
We decided to develop a fully representative optical bench and install the complete optical train and detectors for two of the most extreme channels: UV channel 2 (300-412 nm) and NIR channel 8 (2259-2386 nm), and test it in a thermal vacuum chamber at Dutch Space in Leiden (now Airbus Defence & Space).
The test yielded a wealth of measurement data, gave us the confidence that the required alignment and stability accuracies were achievable. The test also revealed unexpected behaviour of mounts of optical elements at extreme temperatures. It enforced us to redesign and reengineer a number of mounts at a pretty late stage of the project
The SCIAMACHY instrument
The instrument was a passive spectrometer, designed to measure sunlight, transmitted, reflected and scattered by the earth's atmosphere or surface in the ultraviolet, visible and near infrared wavelength region. It was launched on board ENVISAT in March 2002 and operated successfully for 10 years, until April 2012 when ENVISAT was switched off.
Its main purpose was to improve our knowledge of global atmospheric changes and the related issues of importance of the chemistry and physics of our atmosphere. In particular the stratospheric ozone chemistry and the global impact of tropospheric pollution were subject of study.
Space Instrumentation Engineering at TU Delft
Based on my experience in design and engineering of space instruments, I developed a master course Space Instrumentation Engineering at Delft University of Technology, and delivered it in the period of 2006 till 2012. It had a broad range of topics, ranging from sensor physics, sensor anatomy, systems approach to instrument design, geometrical optics and image formation, stray light, image quality, radiometric and spectral performance, instrument calibration, opto-mechanical design including alignment, cryogenic design, contamination and cleanliness engineering, assembly, integration and test, until the operations concept.
For students in this course, the Breadboard model was a fascinating showpiece. I developed a plan to extend the theoretical engineering course with hands-on experimentation, using the SCIAMACHY Breadboard 2&8 model in one of the labs.
Due to a change in position from fulltime lecturer to Director of Education, I transferred my course to a colleague in 2012. Regrettably such test campaign for students never came into being.