We’re members of Solar Probe Plus (SPP), NASA's mission to touch the sun: flight software team, systems engineers, and project scientist. AMAA!

Hi!! What kind of materials could withstand some harsh heat and conditions??

Hello! The heat shield is the main component seeing the Sun. It's made of carbon foam sandwiched between carbon composite sheets with a white ceramic coating on the Sunward side. Other items that see the Sun are made of niobium metal or silicon (solar cells). We spent lots of time developing the technology to withstand the Sun!

- jdk

So it's almost like an advanced version of what you're supposed to do to watch a solar eclipse?

Yep. We use the heat shield to make a shadow. All the spacecraft components and instruments live there and stay relatively cool.

- jdk

What temperatures will it need to endure at that distance (4 million miles)?

About 1300 deg C! (omg)

-sdk

Is the mission to do a very-low-altitude orbital insertion? a very-low-altitude flyby? or just straight up fly into the sun?

The last one would be pretty darn cool, but probably yield less data. haha.

Also, what do we expect to learn about the sun's Corona? Are there extant theories about the corona that will be tested, refined, or proved/disproved, or is this more like new Horzons where we don't really know what to expect.

We'll be flying 24 orbits around the Sun starting at a perihelion (closest approach) of 35 solar radii. We'll use Venus flybys to walk the perihelion down to about 9.8 solar radii, or 4 million miles from the Sun.

There are some mysteries about the corona we hope to solve. One is how the solar wind is accelerated as it leaves the Sun. We know magnetic and electric fields are involved, but the exact processes are unknown. We hope to measure them directly.

And yeah, if we flew directly into the Sun, we'd go out in a blaze of glory!

- jdk

Could you elaborate a bit on what we know (or hope to know) about how solar winds leave the sun?

I have (a little) background in astrophysics, so don't be afraid of using big words. Something something magnetohydrodynamics.

We are going to answer how the solar wind is accelerated. There are many mechanisms that have been proposed but until we can actually get close enough to take in-situ measurements we cannot determine which, if any, are the corrects one(s). - NJF

My 13yo son wants to work on a project just like this someday. He loves this stuff.

He always wants to know,

What kind of educational requirements and pursuits will enable to work in your field some day? Thanks.

STEM !!! Science Technology Engineering and Math! (Also, you could get a degree in philosophy from the UofC - but that's optional.) -AAM

Thanks so much to all who replied. You guys are GREAT. I will show him this. He goes to a great school with great STEM facilities and he focuses on E and the M. His all time hero is NdGT.

He will love that you posted here. THANKS ladies and gents!!!

You are welcome! Good luck to your son on his education! -- CJK

I started out as a physicist, working on radiation effects in spacecraft electronics. Eventually, I got interested in spacecraft systems and moved over in to systems engineering. And now I'm leading the engineering team!

We have engineers of all sorts working on the project - electrical, mechanical, aerospace, software, computer, etc. My main advice - pick a technical field, and then while in college look for internships in the field.

- jdk

That's great to hear! For me, a computer science degree was my path to working on a spacecraft, but building a spacecraft requires many different fields: this includes not only the STEM fields but also business backgrounds to keep track of our budgets, program managers to keep the project moving ahead, editors to help us write coherently (very helpful, I can say!) and many others. I think the best path is to find something you really enjoy and find a way onto a team. (Because I can vouch for the fact it is pretty cool!) -- CJK

When you guys finish super huge and important projects, what is usually your party-drink of choice?

Corona, of course! :) (But preferably a little cooler than our spacecraft will be). -- CJK

We are all very buttoned down engineers that wear suits with skinny ties - so what's a party? -A

Just to clarify, "A" only wears a tie 4 out 5 days. -- CJK

Well, my fave is a mojito!

- jdk

woah dude, how you are not melting?

We have a heat shield called the Thermal Protection System that can handle the heat - it'll be about 1300 C at closest approach. It makes a shadow, and all the spacecraft components and instruments stay about 20 C, or room temperature.

- jdk

what does that badass material look like?

The heat shield core is carbon foam. It basically looks like black styrofoam. The top and bottom face sheets are gray, and have a fabric-like look to them similar to most carbon composites. The top face sheet is coated with a white ceramic material to reflect back as much sunlight as we can.

- jdk

Fascinating. All due to it being space and not having to deal with areodynamics. So, I am safe to say there will be little to no thermodynamic heat transfer around the sheild that could heat up the components?

I just write software, but yes, that's what the TPS is designed to do -NSP

Basically - the sun facing side of the shield will be around 1300 degrees and yet the instruments on the other side will be working around room temperature. - NJF

You mentioned that SPP is going to do 24 orbits around the sun. How accurately do you know where SPP will be during the 24th orbit? Can you estimate within 100 miles of where it will be, 1 mile, 10,000 miles? What software do you use to calculate the spacecraft's path?

Excellent username (solarprobeminus), BTW. :) -- CJK

Some of our team members are mission designers. They come up with the trajectory we'll fly, including Venus flybys and trajectory correction maneuvers - right now, we're planning on something like 42 maneuvers to keep on course. Our plan is to hit our perihelion target of about 4 million miles within 500 miles.

Others of our team are navigators. They use data from the Deep Space Network to figure out where we are and what maneuvers we need to get us where we want to go. As part of this they have to consider effects like solar radiation pressure and forces due to torque control on the spacecraft.

There are several software packages we use to do this work, most standard tools in the space business. These mostly use differential equation integrators to model the flight trajectory, including gravity and relativistic effects, or are Monte Carlo calculations to make statistical corrections to our trajectory. Unfortunately, I can't remember the names of the software packages... :)

- jdk

In terms of specific packages, we use MATLAB, SPICE, and STK. -NSP

Will commands be sent to the spacecraft when it is in the Sun's atmosphere and how long will a command take to reach the spacecraft?

The telecomm plan is actually really complicated and is one of the harder problems we're working on. First, the Sun interferes with the RF signal, so we can't communicate when the Sun and Probe are lined up relative to the Earth. Second, the instruments and the telecomm system can't be operated at the same time due to power limitations. So we take data when we're close to the Sun and downlink the data when we're further away. (except we do occasionally get a beacon tone while we're close to the Sun to let us know things are ok). This is why the spacecraft is so automated.

The worst case light-time is about 16 minutes, when the probe and the Earth are on opposite sides of the Sun.

Thanks for the info. CJK - that was a better question than asking about your blue coats, right?

Indeed! I was wondering about that username. :) -- CJK

I hear that it is routine practice to directly program in Assembly on this large aerospace missions because you can't trust the compiler. So I have two questions,

How much of your coding is done in Assembly? How much time do you save by just directly hardwiring all of your bits?

Actually, on previous missions, we have discovered errors in compilers. Even if you trust the compiler, it is hard to trust that those bits will stay the same in memory in a radiation environment. Which is why flight software spends a good deal of time scrubbing and checking the contents of memory. -Ed

MACROS! MACROS are your FRIEND! -AAM

The call is coming from inside the house! Hi Avi! --Us

Are you excited to be going on such a massive rocket?

How much of a coincidence is it that Solar Orbiter will be launching around the same time? Can you predict any benefits generated by having two spacecraft close to the sun at the same time?

Lastly, and off topic: do you think we'll get another SOHO, or is SOHO immortal?

Yes we are very excited to be going to a Delta IV Heavy - the launch will be spectacular.

Solar Orbiter is currently scheduled to launch a few months after SPP. This will be a great opportunity for us to be able to do collaborative science between the two missions.

SOHO has been an incredible mission and has made so many transformational discoveries. There are several other solar missions up there now which are also doing great science - STEREO, SDO and IRIS to name a few - so you could say that SOHO was the pathfinder for those subsequent missions to follow and build upon - NJF

(Sorry for lengthy response, question is in last paragraph)

Of course, but (ignoring STEREO and its different perspective) SOHO is the only one with a coronagraph, right? It has been nice having the constant views from SOHO and SDO, and I always wonder if a replacement/upgrade mission will happen with the same sort of continuous observations from L1/earth orbit.

But anyways, I have been extremely excited for this mission - my jaw dropped when I first read what the close perihelions would be.

Plasma physics usually goes way over my head, and as much as I can appreciate that it is good science, I really love all the sun images - Hinode, IRIS, all the rest. Are there simulated images of what the view from the Wide-field imager will be, or could you describe them?

Yes we have simulated images - Here

There are many proposals to fly missions that will carry coronagraphs and hopefully one will be successful in the future! - NJF

Really appreciate the responses- last reply from me: So there are two telescopes that will be nominally pointed just like that?

Any hopes to do some planetary science on the way past Venus?

Sorry, regarding your first question, I'm the last one left closing out any unanswered questions and I'm just a software guy! However, for the second, NJF answered below: "We are not planning to do any Venus science as the instruments will be turned off for thermal and power management during the flybys."

First of all good luck and big respect, my question would be how much of the tasks are automated ? i work in automation :p

The reason this took so long to answer is that NSP took the time to write a meta-script that answers questions of this sort in general. -A

In terms of how we build the spacecraft and write the software, or in terms of what the spacecraft will do during the mission? Personally, I automate as much as possible in terms of what I'm assigned to do.

The spacecraft itself is also extremely automated. All pointing and trajectory corrections are commanded at a high level (e.g. "keep the thermal protection shield pointed at the sun", "point antenna to the earth"), and the software works out the details. We also let the probe autonomously adjust the solar panel positions, to get enough power without overheating.

All of this is separate from what we call the Autonomy software, which is continually monitoring the spacecraft for signs of things going wrong, and will take corrective action to keep things working as well as possible.

-NSP

How often do your friends and family bug you with sexual inuendo's regarding "Probe Plus"?

In all seriousness, Science rocks! Never stop exploring and asking questions! Keep up the great work.

Hey, at least we're not going to the seventh planet with this name ;)

When will you get mentioned on The Big Bang Theory? ;)

Serious questions: 1. What programming language(s) do you use?

2.) How does a university student make the right choices (classes, internships) to be involved in your line of work?

Thank you! Success to you and the project!

Well, some of us worked on New Horizons, which featured prominently in an episode, so we have high hopes for another appearance! :)

As far as choices? Study an engineering discipline, take lots of math, work with a professor in research, do an internship with us!

- jdk

Focusing on STEM fields (Science, Technology, Engineering, and Math) will move you in the right direction. Johns Hopkins Applied Physics Laboratory offers NASA affiliated internships - visit our web site.

NOT assembly!

I can answer that specifically for flight software. Working with embedded systems is an intersection between computer engineering, electrical engineering, and computer science. We like to see people who have written software running on custom hardware, and people who have experimented with custom hardware platforms. _Ed

What language(s) is the flight software written in?

NOT assembly. -AAM

At some point, isn't it all assembly? -Ed

MACROS! MACROS are your friend. -AAM

bincsh - Sorry for the facetious answers. On the New Horizons AMA someone asked the same question and someone (a scientist!) answered assembly. That became an in-joke around the flight software group.

C with a little assembly. -- CJK

I'd surely love to take a peek at its internals. Is the code by any chance open source?

Yup (edit: some of it). We use the Core Flight Executive (cFE) developed by the NASA Goddard Space Flight Center as middleware. GSFC has released that software as well as several apps that run on cFE called Core Flight Services. Here's the press release on that:

https://www.nasa.gov/press/goddard/2015/march/nasa-goddard-releases-open-source-core-flight-software-system-application-suite-to

-- CJK

The SPP source code itself is not open source. But, there is a fair bit of open source code provided by NASA on http://code.nasa.gov. -Ed

The vast majority of our flight software is written in C. Some of this software is auto-generated from a template. Some of it is auto-generated from higher-level languages such as Simulink. Some of our software implements engines that can be configured in cases where we need to change spacecraft behavior without uploading a new code image and rebooting. -Ed

Sounds really interesting; with those goals in mind, what use will that information be going forward?

Just to underline an important point, the corona is the sun's "atmosphere" and yet, counter intuitively, it is HOTTER than the actual surface. This is a very puzzling phenomenon, and if we can find an answer we may gain an important new understanding of thermal dynamics. -A

The information from the mission will help scientists to answer questions that have been top priority for over 50 years. Why is the corona hotter than the surface of the Sun and how is the solar wind accelerated? - NJF

Thank you! If those questions are answered, will that satisfy a scientific curiosity, or are there other benefits to those answers? Can knowing those answers benefits humankind in any way that's already been thought of?

There are many benefits to the answers - the Sun is our star and we live in its atmosphere. When the Sun emits a flare and or coronal mass ejection, billions of tons of material and high intensity particles are accelerated - these can be directed towards Earth and can cause havoc for spacecraft, communications and power systems etc. Until we can fully understand how our star works, we will not be able to improve our ability to predict these events and their effects on Earth - NJF

What is your opinion of the movie Sunshine?

I hadn't heard of that until you mentioned it. I'll have to give it a look. (Although naming a spacecraft that's flying to the Sun Icarus seems a little ominous!) -- CJK

What's your biggest achievement so far?

For me, getting the heat shield through design and technology development. Imagine building a 10 foot slab of styrofoam that can get heated up to 1300 C, then shake the crap out of it to make sure it'll survive launch. And it worked... :)

- jdk

SPP is a mind blowing mission and one of the most exciting things you could ever hope to do. Every technology development is a huge achievement. However, I agree with JDK - our heat shield is our "shining" achievement so far - NJF

The flight software team completed Build 1 of our software last month which would be our biggest achievement thus far. Now we're working toward Build 2 which is targeted for release in January. -- CJK

Did you reuse code from New Horizons or MESSENGER?

Only the assembly code. -AAM

What?? I didn't realize we were getting second hand stuff!

Yes. We use software from New Horizons and MESSENGER as well as code from other previous missions such as the Van Allen Probes. When something works, we like to reuse it! -- CJK

When can we expect SPP to reach the sun?

We will make our first close approach about 3 months after our launch - launch date is July 31, 2018 - NJF

When is the launch (I'm too lazy to look it up!)

Launch is at 3 AM. You're going to have stay up late or get up early! - CJK

Yep - we are going at night!!

The launch period starts July 31, 2018, and is open for about 20 days. 6 weeks later, we'll pass by Venus for the first time. 6 weeks or so after that we'll pass through our first perihelion. We'll continue this pace for 7 years! For closest approach, we make perihelion passes every three months.

By the way, this is a pretty fast paced mission... :)

ETA: ooops, wrong year for the launch date!

- jdk

FYI - "Perihelion" is the term for the closest approach to the Sun - "peri" meaning "close" and "helion" meaning the Sun. -AAM

The first time we get to our closest distance from the Sun (less than 4 million miles) will be Christmas of 2024 - what a great Christmas present for the scientists!! - NJF

What is the heat shield made of, and is there going to be a LEGO set of the spacecraft?

There is already a Lego version of the SPP spacecraft - NJF

The heat shield core is carbon foam. It basically looks like black styrofoam. The top and bottom face sheets are gray, and have a fabric-like look to them similar to most carbon composites. The top face sheet is coated with a white ceramic material to reflect back as much sunlight as we can. - jdk

Can you tell us about your photographer? Those pictures look great!

He's a bit of an artistic troublemaker, but because of his fine work, we keep him around. ;) I hear he's going to make it big soon with a video about New Horizons. -- CJK

How close would you go, if not very close, any plans on bringing it back?

We are going close and bringing it back 24 times!! We will get to within 4 million miles from the Sun and complete 24 orbits - NJF

As we orbit the Sun, we use 7 Venus flybys for gravity assist to get closer as we go. A side effect of that is that our aphelion (the furthest distance from the Sun in each orbit) gets lower after each flyby. So by the end of the mission, we'll only get about 0.7 AU from the Sun, or about the orbit of Venus. It'll never come back to Earth... - jdk

Will you get a chance to do much Venus science during the flybys? Thanks and good luck!

We are not planning to do any Venus science as the instruments will be turned off for thermal and power management during the flybys - NJF

Hey guys!

I'm a second year aeronautical engineering student at Clarkson university, and have always been interested in what NASA and others have been able to do.
How did you all get hired? And how would someone looking to get into the field go about finding a job/internship?

Go to the jhuapl.edu web site and apply. RMF

I was hired by a campus recruiter that visited Michigan State University while I was in graduate school. Others were hired as interns, then stayed after graduation.

Head over to www.jhuapl.edu and look at the job board. Our intern postings are there, and we usually hire on order 40 interns every summer.

- jdk

If you get a chance to go to a big conference then this would be a great opportunity to network with companies and universities about prospective opportunities. Otherwise most universities advertise internships on their websites. Internships are one of the best ways to get experience while you are still a student and this will give you a more complete resume when applying for jobs - NJF

Always good to hear from future engineers! I worked for ten years or so for the federal government. After that I moved on to a small space software company for about a year then applied to APL. (Not the first time, I might add! Persistence is helpful.) They brought me in and I interviewed with a few folks and then was hired.

There's a couple of paths to finding a job here. One is through applying to the website, another is if APL is doing a campus visit. (I'm not sure if we visit Clarkson). We also have at least four internship programs at APL that I know of. One is our ASPIRE program for high school kids (a little late for you :), a NASA internship program, an Advanced Applications Scholars program, and a program for students from Historically Black Colleges and Universities (HBCUs), Hispanic-Serving Institutions (HSIs), and Minority Institutions (MIs).

Here's the intern link:

http://www.jhuapl.edu/employment/summer/

-- CJK

Everyone's story is different. I gave them my resume every year at my school's engineering career fair. I never even got a call for an internship, until I put InControl on my resume in my senior year (because I got a chance to use it on CUSat), and landed my current position. -NSP

You guys seem to have a great team dynamic. Are there any fond memories that you have with one another that you would like to share?

This AMA is becoming one of the best team memories. :) Thanks all for helping us make it that way! In addition to today, I find the best team memories are when we are approaching a big review where have all of the subsystems working to a central goal. When the review day comes, we each go up in front of the panel with so many people behind us as support. It reminds me a lot of when I was part of my swimming teams so many years ago. It's a lot of work to reach the goal, but in the end it's worth it!! -- CJK

Working on SPP is a great experience and we all love what we do. The team is amazing and I think that we all feel privileged to be part of it. - NJF

Are all the instruments protected by the heat shield?

No - the Solar Probe Cup sticks out beyond the heat shield and samples the bulk of the solar wind coming directly towards the spacecraft. This one is "hanging out in the breeze" feeling all the heat and power of the Sun. Also, the radio antennae reach beyond the heat shield so that they can sample the turbulence in the solar wind. Both of these instruments have had to go through rigorous testing to make sure they will survive the journey around the Sun - NJF

Could you use cardboard as a TPS and, if so, where can I buy some?

We can absolutely use cardboard as a TPS. The important question is for how long could we use cardboard as a TPS! -Ed

Can you tell me a little bit about the science instruments that are being used on the mission? What's your favorite one and why?

We have a very comprehensive set of instruments which will make all the measurements necessary to fully characterize that solar environment close to the Sun. Highly energetic particle telescopes, plasma detectors, magnetic and electric field instruments and a white light imager.

Can't pick a favorite - I love them all equally :) - NJF

Hey guys! Thanks for doing this! Three questions: How does one heat up a 10ft shield to 1300 C? Also, are there any moving parts on the spacecraft? Are there any secondary objectives, such as taking some data while flying by Venus?

We are not planning to do science at Venus since the instruments will be switched off for thermal and power management. We are very much a voyage of discovery so new questions and mysteries will surface during our journey - NJF

We have only 3 things that will move throughout the mission: the two solar panels can rotate on two axes each (to get more power and cool off, depending on how close the sun is), and the high gain antenna rotates back and forth to point at the earth and downlink science data. You might also count the water flowing throughout the solar array cooling system (and the pumps that move it), and then I suppose you'd also have to count the propellent in the fuel tank, and the thruster valves as they fire.

We also have some things that will only move one time, shortly after launch. We call them "deployables": 4 electric field antennas, one camera door, and the long magnetometer boom. -NSP

So how approximately long would it last if the attitude control system suddenly stopped at perihelion?

If the attitude control system stops at any time in the mission, the computer that had been in charge will be demoted from that role and a "hot spare" back-up computer will take-over within one second and we'll keep flying. - sdk

Serious questions:

1.) How soon after launch will you start collecting science?

2.) What is the end of life plan?

3.) Can you tell me the difference between SpaceWire and SpaceFibre and why you're using one over the other?

SpaceWire uses conductive wire cables while SpaceFibre uses fiber optic transmission. The wire is LVDS - same as USB - SpaceFibre is the same as Verizon FiOS. The same SpaceWire protocols are used over both.

SpaceWire is tried and true technology, while SpaceFiber is still developmental, so we are going with SpaceWire.

We will start collecting science during our first solar flyby just 3 months after launch - NJF

You mention your software is mostly written in the C language. Do you follow a software development approach? I hear a lot about Agile Development lately.

Agile is used on smaller, more experimental projects - we don't generally use that approach on large high stakes programs. -AAM

Slight correction: the project doesn't necessarily have to be experimental, just more amenable to the more iterative Agile methods. Many ground software tools are developed in a scrum or kanban or other process, because it is possible to release a version of the software to users every few weeks, and incorporate feedback into the next release. It's a bit harder and more expensive to launch a satellite that often, just to debug. -NSP

SPP flight software uses an incremental waterfall development approach. Starting with requirements development followed by preliminary design, detailed design, implementation, designer testing, and independent acceptance testing. RMF