Meet the Team: Dr. Harold Reitsema

Caleb Castle

December 4, 2014



Harold Reitsema’s Bio:

Harold is a planetary astronomer with more than 30 years experience specializing in the design and building of interplanetary spacecraft and astronomical imaging detectors. During his tenure at Ball Aerospace, he led design teams for Hubble Space Telescope, was the principal investigator for NASA Planetary Instrument Design, the Flight Project Manager of the Sub-millimeter Wave Astronomy Satellite instrument program, and lead systems engineer in support of science teams for several NASA science instrument programs, including the GIOTTO mission that flew past Halley’s Comet in 1986, and discovered satellites of Saturn and Neptune.

Harold has published more than 50 papers in the areas of astronomy, planetary science and space missions including studies of asteroids and planetary satellites. He also received a U.S. patent for the Optically Coupled Shaft Encoder. He has a Ph.D. in astronomy from New Mexico State University and is a member of the American Astronomical Society, American Association for the Advancement of Science, American Institute of Aeronautics and Astronautics, and the International Astronomical Union; and is listed in Who’s Who in America. Asteroid 13327 Reitsema is named in recognition of his contributions to Planetary Science. Harold enjoys railroads, Southwestern archaeology and sailing, and lives with his wife in Holland, MI. He has two daughters.

The Interview:

What do you find most exciting about the Sentinel Mission?

For me, the most exciting part of the Sentinel Mission is that it combines my experiences with planetary science and NASA science mission design into an opportunity to achieve a mission that will make a real difference to the future of humans and our civilization. Asteroid impacts are probably the only natural disaster that can be prevented, and Sentinel will give us the advanced warning that is required to deflect the threatening asteroid.

How did you become involved with the Sentinel Mission Leadership Team?

While I was still working at Ball Aerospace I realized that the technology already existed to build the spacecraft and infrared telescope that would be able to find the threatening asteroids. I assembled a design team that did the conceptual design for such a mission. I worked with multiple NASA offices for several years to attempt to generate interest and support for the mission without success. Shortly after I left Ball, Ed Lu contacted me with his suggestion that we adopt that mission as the objective for B612 Foundation.

How will the Sentinel Space Telescope perform over the life of the mission?

The Sentinel telescope observes in the infrared wavelength region where Near Earth Asteroids emit signals that are easily detectable with a space telescope. While the asteroids are typically very dark – like charcoal – their dark surfaces absorb much of the sunlight that falls on them, warming them and increasing their infrared emissions. Unfortunately, infrared light is absorbed by water vapor in the Earth’s atmosphere so the only place to perform an infrared survey is space.

We will put the telescope in an orbit around the Sun far from the Earth. In such an orbit, it makes its trip around the sun much faster than Earth, and also faster than asteroids that are nearest the Earth. This gives the observatory multiple chance to find the asteroids that are at too large a distance from Earth to be seen by ground-based telescopes.

The Sentinel telescope will not only be able to find the threatening asteroids but it will also map out their orbits so that we will know where it will bo for the next century. With this information, we can find asteroids that have a risk of colliding with the Earth. With a decade or more of warning, Earth can build and launch a mission that will deflect the asteroid away from its impacting path.

What would you like people to understand about the Sentinel Mission?

The most unique feature of the Sentinel Mission is that it will be able to provide highly accurate orbits for analysis of future threats. By virtue of its Venus-like orbit and its 6.5-year lifetime, it will see most asteroids multiple times, whereas ground-based or Earth-orbiting telescopes can only see an asteroid during their infrequent close passes by the Earth.

How does a planetary astronomer end up building telescopes and spacecraft?

As a planetary astronomer, I was always able to find a better way to build an instrument to get the maximum performance. This led to good research results but also developed an interest in me to work with the best technologies and the best engineers. This took me to Ball Aerospace, where I was able to work on science missions that required the very best instrumentation. I was fortunate to be able to participate in missions like the European GIOTTO mission to Comet Halley, NASA’s Spitzer, Kepler, and the Deep Impact mission that demonstrated technologies for asteroid deflection. I was also involved with seven instruments for the Hubble Space Telescope. My role as Mission Director for the Sentinel Mission is a great opportunity to apply this experience to a mission that has intrinsic safety value for humans.

Tell us about one (or more, if you wish) of the most memorable moments in your career.

Two of the most memorable events in my career were the GIOTTO flyby of Comet Halley and the Deep Impact delivery of a probe to the surface of Comet Tempel 1. Both were very difficult and challenging missions whose success was far from guaranteed. So it was thrilling to see the spacecraft images that were returned, proving that the missions were a success. Fortunately, the Sentinel Mission is a much more sedate mission without the navigation challenges of a comet rendezvous.

Who are your inspirations?

I have been very fortunate in my career to learn and work with some very interesting, energetic and inspirational people. By knowing these people well I was able to see what inspired them, and found many habits and goals that also worked for me. And it is a humbling experience to work with an interdisciplinary team such as is required to pull together a successful space science mission.

What do you like to do when you’re not working on Sentinel?

My wife and I like to travel, visiting our daughters and seeing new places around the world. We are always challenged between adding a new destination and revisiting the many places that we have enjoyed. Beaches seem to be a recurring theme.

What’s on your bucket list?

I haven’t been on an African safari, so that is high on the list. And I have thought for years that I would enjoy building a model railroad but haven’t gotten down to starting. And of course, Sentinel!

Last question: Star Wars or Star Trek?

Easy, the early Star Wars trilogy. I have a hard time watching Shakespearian acting, and aliens with chlorophyll for blood is just too much.

Caleb Castle