Opening a Fancy Gold-Plated Parasol in Space

Here it is! A guest post from the resident rocket scientist himself. Jonathan, my husband, mechanical engineer at Jet Propulsion Laboratory, giving you all a glimpse of the crowning glory moment of a spacecraft.

Five weeks ago began the most exciting, nail biting, 48-hour period I’ve had to date in my career at JPL.

I was on vacation, when I received an early morning phone call that it was time to deploy antenna on orbit a week earlier than planned. It was actually one of those weird “precognitive” experiences, where I was dreaming that a decision had been made to deploy the antenna, several minutes before waking up to the phone call. No big deal, only a project I’ve been working on with the rest of the team back at JPL for the past five years, my entire career thus far, at JPL. All that needed to be done is push an antenna out of a tiny 10 cm diameter canister, and deploy it to 510 mm, with a surface accuracy of 0.2 mm. Now, while some may wonder what is so hard about opening this gold-plated molybdenum upside down umbrella in space, the 0.2 mm accuracy we had to achieve across the entire deployed surface, is the same as the thickness of a business card. It was a daring technological endeavor, but one that would enable the first Radar in a CubeSat.

As you can imagine, instantly I was out of vacation mode, and into work mode. What proceeded were a series of teleconferences between my colleagues back at JPL, the spacecraft operations team at Tyvak, and myself. We decided to schedule the deployment later in the day on July 27th. The pre-deployment checkout commands were uploaded to the spacecraft, and then began a long waiting period until we had our next spacecraft downlink. (Remember you can only talk to the spacecraft when it is over an antenna, and given it takes 90 minutes per orbit, and you aren’t always over a ground station. Long waiting periods between sent commands and seen results are the norm.)

As soon as the data was downlinked, I started reviewing the motor telemetry CSV file to see if we were good to go. Motor proportional term, nominal, current limit, nominal, integral term, nominal… and down the list I went, everything checking out as nominal, until I got to the final parameters. Position limits… not nominal… if we were to deploy with the position limits activated in their current state the deployment would stop short.

This resulted in another set of teleconferences with the ART (Anomaly Resolution Team), and the discovery: while the position limits had been set before launch, the values had only been saved in non-static memory, which means the system defaulted to the old values when the power was cycled. A classic case of the computer doing exactly what we told it to do. After discussing this further, because we deactivate the position limit prior to deployment, it was determined that these values, even though they were not what we were expecting, would not inhibit deployment operations. Unfortunately, because of the additional time required to discuss this anomaly, we missed the window to deploy the antenna. We would try again tomorrow.

It was about this time I recognized the “real” problem. Because I was on vacation, I had forgotten to have any lucky peanuts on hand. Of course we ran into an anomaly without any lucky peanuts available. (Another piece of background, lucky peanuts are a tradition before any JPL critical operation, a long held tradition). I searched the house and raided the pantry where I was staying. No luck, just peanut M&M’s… and I don’t think those count. So, it was a 20 minute drive to the closest open grocery store to pick up some lucky peanuts for the next day (okay, the trip was not just for the peanuts, there were a few other supplies needed).

Saturday morning, July 28th started with another round of teleconferences. While chowing down on my lucky peanuts, we discussed the ground station passes during the day. We decided the deployment would be scheduled for later in the afternoon, just before a ground pass so we could downlink data after deployment to confirm success. Prior to uploading the commands, everyone on the teleconference confirmed their agreement with the plan. Mission PI… GO, Project Manager… GO, Mission Manager… GO, Spacecraft Operations… GO, Quality Assurance… GO, Antenna Mechanism Engineer (that was me)… GO. We were GO for deployment!

Now it was just a waiting game. The software was written, the code was set to be uploaded on the next ground pass in an hour, and then the deployment was scheduled for several hours later. Those were some of the longest hours of my life, thinking about all the things that could go wrong in this critical operation. What if the mechanism jammed, what if the software code was incorrect, what if the motor controller received a direct hit by a high-energy, radioactive particle right as we were deploying creating a single event upset. While we had performed dozens of tests to qualify the antenna on the ground, ensuring it would work in the space environment, my engineer mind could not help but think of all the potential ways something could go wrong.

Finally the time came. At 6:45 pm, I called into the spacecraft operations center at Tyvak, about 15 minutes before the ground pass. If everything was nominal, the antenna would be deploying right now, and we would know about it a few minutes later. Five years of my life, and the rest of the team who developed this antenna, had all come to this moment. If successful it would mark and amazing accomplishment, and if not, it meant the next few weeks and months of my life would be consumed with meetings and reviews, starting with Anomaly Resolution Team and ending with a full-fledged failure review to senior management. I was eating as many of those lucky peanuts as I possibly could.

At 7:56 pm, the data was downlinked. I logged into the secure server, to review the data. The first data set was extremely minimal. Because we were communicating over UHF, all that could be downlinked was a limited set of current data (taken once every 10 seconds over the 3 minute deployment) and the conditions of the limit switches which were supposed to activate if the motor reached its final position. Upon opening the file, everything looked correct. Motor current draw was nominal, and switches were closed, indicating the antenna had deployed. We had preliminary confirmation of deployment, but couldn’t declare complete success yet. We needed more data.

As we were waiting for the next data pass, a number of scenarios were going through my mind. Maybe the antenna deployed, but the mesh and ribs didn’t open fully. Or what if the antenna deployed but had been damaged during launch. There were any number of worst case scenarios where the data set I had may not fully confirm deployment.

Finally, several hours later the next data set came in. This data set contained the motor encoder telemetry and showed that the motor reached its final position. All telemetry made this appear a nominal deployment. But there were still any of number scenarios I could imagine, where things could have gone wrong. What I was really waiting for was a picture from the camera onboard the spacecraft showing an image of the fully deployed antenna. Of course, given images are large files, it would not be downlinked until the S-band pass later that day.

I went to sleep that night, wondering if the image would confirm a fully successful deployment. Or, in my worst nightmare, would we see an antenna with the subreflector stuck down around the horn, preventing any RF energy from escaping, effectively making this mission useless. I should note, while the chances of this happening were essentially zero, and nothing like this had every occurred in the dozens of test we had performed on the ground, my engineering mind could not be prevented from catastrophizing the situation.

Sunday morning I awoke, and the first thing I did was check my email. No data yet.

At 9:03 AM my phone vibrated, indicating an email was received. I instantly opened the email app, knowing this would either confirm my hopes or the nightmare. It had been such an unexpected roller coaster over the last 48 hours, with information taking so long to come down from space, making me wonder if it was successful or not. Could all the positive indicators just have been a cruel trick, making me think the antenna had deployed successfully?

I opened the email on my phone.

I saw there was an image attached.

I opened the image.

I saw the dark background of space, with a blue globe underneath. Partially obscuring the globe was a beautiful gold mesh surface, an antenna fully deployed.

That’s what the team and I had been working on for the last five years. What an amazing confirmation that everything had worked. We even overlaid a picture of the antenna as deployed in the lab (see lower inset), which confirmed the deployment on orbit perfectly matched the deployment in the lab. My worst nightmares were put to rest. It was then finally time to share the successful deployment with the rest of the team, who had put in so many hours on this project. I could confirm that our hard work had paid off. Several hours later, we received a video of the antenna deployment, confirming the operation in all its glory.

But the most exciting thing is that this was only the start of the RainCube mission…

 

That’s my man, guys! Way to go, RainCube Team! Congratulations!

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