“Per Aspera Ad Astra:” The Complexities of Operating SOFIA

Every year, NASA’s airborne observatory SOFIA takes off about a hundred times to help scientists gather data to better understand our solar system and the rest of the universe.

Each of those flights, however, starts way before the heavily modified Boeing 747SP gets in the air. Each of them involves getting a large amount of moving pieces to come together perfectly. Each of them can be described by the Latin phrase “per aspera ad astra” or “through hardship to the stars.”

In this article, I will take a look at what is involved in getting SOFIA off the ground in a meaningful way – in a way that helps us advance the boundaries of our knowledge of the universe.

NASA SOFIA Observations
SOFIA mid-infrared image of the Milky Way’s nucleus on the left and a visible and near-infrared image on the right. As demonstrated by the images above, among other things, SOFIA can see through the opaque dust in the plane of the Milky Way. (Photo credit: [left] NASA/DLR/USRA/DSI/FORCAST Team/Lau et al. 2013; [right] NASA/ESA/STScI/AURA)

This is the third article in a four-part series detailing the history and operations of the world’s largest airborne observatory, Stratospheric Observatory for Infrared Astronomy also known as SOFIA. The following articles are included in the series:

  1. Introduction: Experiencing SOFIA’s Southern Deployment 2018 in Christchurch – An introduction to the series giving an overview about my experiences with SOFIA.
  2. From a Learjet to SOFIA: A Brief History of the World’s Largest Flying Telescope – A brief look at the history of airborne astronomy and a look at how SOFIA came to be.
  3. “Per Aspera Ad Astra:” The Complexities of Operating SOFIA – A detailed look at the variety of teams involved in the operation of SOFIA and the challenges faced by them.
  4. NASA 747, Cleared for Take-Off, Destination Mars: Observing a SOFIA Mission – A briefing-to-landing account of my flight onboard SOFIA.


Time Is the Most Valuable Commodity

There are hundreds of astronomers dreaming of one day being able to use SOFIA to gather data for their research. Unfortunately, because the available observation time is limited, not everyone will get to do so.

As such, just as with getting observation time at popular ground-based observatories, the whole process starts with groups of scientists led by Principal Investigators (PI) devising experiments and then turning them into proposals explaining the experiments’ goals, observation methods, and so on.

Those proposals then go through a peer review process at the end of which the SOFIA Science Mission Operations (SMO) Director chooses the projects which get observation time and budget, and ranks them on the scale of “will do” to “do if time.” SOFIA has an over-subscription rate for observing time of 4:1 – meaning there are four proposals that are not selected for every one that is awarded time on the telescope.

While the above process is run by the USRA (Universities Space Research Association) for NASA, it is open to all US and international scientists. There is also a similar process conducted by DLR, NASA’s partner on the SOFIA project, which is open to members of the German scientific community.

Separately from the above, there is also “Director’s Discretionary Time” where the SMO Director can approve certain projects without the need of going through the proposal process.

Translating Celestial Objects to Longitude and Latitude

With the selection process complete, SOFIA’s flight planners get into action.

It’s their job to take research briefs that are based on “celestial navigation” (i.e. we want to lock on this and that tracking star and observe this and that celestial object) and turn them into flight plans that the pilots and air traffic controllers can reference.

SOFIA Flight Plan
Each of the legs of a SOFIA flight plan is a curve to adjust for the fact that the Earth is rotating. (Credit: NASA/SOFIA)

When doing so, there are several things that the flight planners need to consider.

Because SOFIA’s telescope can only be operated with one instrument at a time and changing the instruments is a labor-intensive, two-day process, one of the main criteria that the flight planners have to take into consideration is the instrument required for each of the selected experiments.

Other than that, things such as when the observation needs to be made, how much time is required to finish it, and where the observation has to be made from are taken into account. That is especially critical in the case of observing occultations – eclipse like events where it’s important to be in the right place at the right time, often to the precision of just several meters and seconds.

With all of the above and much more in mind, the flight planners create flight plans that are designed to maximize “science time” for each of SOFIA’s hundred or so flights a year.

Getting the Observatory Ready to Fly

In addition to deciding which observations to make and how to execute them, it is important to get the aircraft itself as well as its telescope and instruments ready to fly.

When it comes to maintaining the telescope and instruments, the science ground operations team takes care of that. Their responsibilities range from “quick” pre-flight checks all the way to re-coating the mirror if necessary (it hasn’t been done yet since the the time the mirror was coated the first time). This group is also responsible for changing instruments when necessary, a process that can – as mentioned in the previous section – take a couple of days.

As for maintaining the aircraft itself, there is a group of in-house technicians that take care of the lighter maintenance checks and repairs. On the other hand, heavy maintenance is handled by Lufthansa Technik in Hamburg where SOFIA is flown every several years.

You can learn more about the challenges involved in overhauling an aircraft like SOFIA in this paper written by some of the people involved.

SOFIA Undergoing Maintenance at Lufthansa Technik
SOFIA undergoing maintenance in the Lufthansa Technik hangar at Hamburg airport. (Photo credit: SOFIA / DSI)

Executing the Missions

All of the preparations above culminate in the hundred or so missions that SOFIA flies every year. About three quarters of those are flown from SOFIA’s home base, Palmdale, and most of the other missions are flown out of Christchurch during the aircraft’s annual Southern Deployment.

Given that the next (and final) part of this series will take you onboard a SOFIA mission that I had a chance to observe in New Zealand in great detail, here I’ll only take a quick look at the teams and people involved in executing the missions.

On the main deck, two mission directors are responsible for coordinating between the flight crew and science teams, as well as for overseeing the mission overall.

NASA SOFIA Mission Director
SOFIA’s mission directors are responsible for coordinating between the flight and science crews.

The flight crew is stationed in the cockpit on the upper deck of the aircraft. Given that SOFIA is a classic aircraft, besides a pair of pilots, there is also a flight engineer onboard each of the flights.

Back on the main deck, near the telescope and its instrument, the science teams have their workstations. Telescope operators make sure the telescope is up and running, focused, and locked on the right tracking stars. Instrument scientists make sure that the instrument is operating without any issues. And, scientists whose experiment is being conducted make sure the data that is being collected is useful.

Separately from the above, on some of the flights, SOFIA’s communications team can be found escorting guests and media.

NASA SOFIA Telescope Operators
A pair of telescope operators monitors the performance of the telescope throughout the flight.

Pushing the Boundaries of Our Knowledge

Once the flight is back on the ground and the data is collected, the scientists get to analyzing the results.

The data remains proprietary to the science teams for one year after it is collected. This allows them to conduct any analyses and publish any findings that came out as a result of their experiment.

Then, however, the data enters the public domain and everyone can access it. In fact, it is not uncommon for important findings to be made by scientists that have never set foot onboard SOFIA or inside the observatory where the data they used was collected.

This system gives the team that proposed the experiment the chance to be the first one to publish results.

But, it also gives a chance to those that did not have a chance to work with SOFIA (or other major observatory) directly to reap the benefits of the data it collected and to push the boundaries of our knowledge of the universe as far as possible.

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