# When was Lucy's mission first scripted in Excel and why is that what Lockheed Martin chose to do it with?

Years before Lucy took off, Lockheed Martin mission architect Brian Sutter used Excel to chart the mission’s path and choose which of the about 5,000 Trojan asteroids the spacecraft should visit.

“Part of the science of this mission was to try to look at as many of these Trojans as we can in a single mission,” Sutter told CNBC.

While Lockheed Martin has a “high fidelity” tool to run individual trajectories, Sutter said that would have taken “forever.” He instead turned to an Excel macro, which is “perfectly suited for sorting through large quantities of data.”

“I had already found a trajectory that connected two of the asteroids to a trajectory that also connected to Earth,” Sutter said.

**Orbit propagation – or modeling the future location of objects in space – “is what I do,” Sutter explained. While his macro consists of “different equations than you’d normally put into Excel,” he emphasized that “at the end of the day it’s all math.”

Sutter took a broad list of 750,000 asteroids and entered them into Excel to “see if they ever accidentally kind of come close to each other.”

“I think this thing took about 12 hours to cycle through all 750,000 of them,” Sutter said. After he ran the macro, he had “a little list of 10 to 20 asteroids that the spacecraft was going to be flying close to.”

His use of Excel to help chart Lucy’s trajectory became famous within Lockheed Martin. He recalled that a colleague once described to others that Sutter “built the most ridiculously complicated Excel spreadsheet I’ve ever seen in my life.”

Hmm...

I've used Excel for scientific numerical computing myself, but it was 20 years ago, and because I was in a pinch and had nothing else available. Now that python/numpy/scipy are so universal I can not imagine why someone would turn to scripting in Excel rather than scripting in Python.

Excel can't even get Bessel functions to better than five digits (not that you'd use Bessel functions to calculate trajectories; just sayin'...)

Question:

1. How long ago was this? When was Lucy's mission first scripted in Excel?
2. How many asteroid were considered; about 5,000 Trojans or "a broad list of 750,000"?
• Both Excel and the standard Python implementation use IEEE 64-bit floating point math operations internally; if Excel’s Bessel function is broken that doesn’t speak to any inherent problem with Excel. 99% likely that Sutter was simply more familiar with Excel than Python, and for a one-off job that was just identifying candidates for further study, it got the job done. Oct 19 at 17:52
• This is not at all surprising. Many years ago, I took a shot at climbing the management ladder. In the process I became intimately familiar with Excel. I found that management was not my cup of tea; I would much rather be doing technical work. I intentionally found a way to get back onto the technical ladder. There are lots of managers who are intimately familiar with Excel. It often is their go-to tool. When they do get the rare chance to do technical work, they'll often do it in Excel. With the hours they work, they don't have the time to learn about python/numpy/scipy, whatever. Oct 20 at 1:30
• The last question, the one you appear to be most interested in, is completely separate from the other two. And the answer is simple: Internal Research & Development (or possibly Bid & Proposal). NASA did not pay Lockheed-Martin to come up with the design. Oct 20 at 2:12
• @DavidHammen okay sold! I'll split off "Why was the spacecraft builder also the mission architect?" as a separate question, will take some time to refactor it, perhaps generalize a bit. Perhaps something like "Did aerospace companies every pitch deep space science mission designs to NASA? If so, what are some notable examples?"
– uhoh
Oct 20 at 2:26
• Sometimes management can have tunnel vision & not realize that doing things smarter can sometimes be an opportunity to make even more money. As for spreadsheets, a friend of mine still uses a complex spreadsheet he initially started in the mid 1990s when he was using Lotus 123. I can still remember him complaining how he had to reestablish it in Excel over 20 years ago.
– Fred
Oct 25 at 21:38