Tag: Training

Science Instruments – Repair vs. Replace

Recently, several people asked: Why not replace the two instruments we’re repairing with new ones and why can’t we take the two science instruments inside the Shuttle and work on them there?

This is such an excellent question! The answer is truly an engineering marvel, so thank you for asking.

Hubble’s instruments were designed for easy removal and astronauts have removed radial and axial instruments on previous repair missions to Hubble. So, why aren’t we doing the same thing this time? Time is the answer.

The most valuable commodity on-orbit besides the astronauts themselves is the astronauts’ time. Every second of their time is choreographed more closely than an Olympian’s gymnastic floor exercise. Just as the gymnast’s every motion is fixed in her or his mind, the astronaut’s every motion outside the Shuttle is practiced so that a moment is not wasted.

When the spectrograph, STIS, failed, engineers led by Mike Weiss at Goddard, looked at every possible way to fix it, including the ones you’ve mentioned such as bringing it into the Shuttle Cargo Bay. But Mike found that “this approach would have taken about 2 additional hours of EVA time and would have required additional hardware to serve as a work bench. Pulling out the entire instrument would also mean overcoming potential contamination and electrostatic discharge concerns.”

I can’t resist taking this opportunity to talk about the symbiotic relationship between humans and their almost-robotic tools one more time! The NASA engineers surmounted yet another hurdle with tool design. If you’ve pulled electronics boards out of your computer, you’d think it might be pretty easy to do on-orbit. But Hubble has something called “wedgelocks” to make sure the electronic boards don’t rattle around on-orbit and so that there’s a path for heat to sneak out, keeping the boards cool. Imagine how frustrating it would be to pull out a stubborn electronics card in bulky gloves on Hubble! Resorting to swearing is usually the path we earthlings take on the ground. Somehow, it always helps, but it won’t help much on-orbit with Hubble.

So, NASA developed an extraction tool to neatly pull out a board. That tool was tested with the most stubborn test board ever made, and came out with flying colors and little debris.

Now that we know how to gain access to failed cards inside the instruments, pull them out and replace them, and put on a new simple cover, our marriage between tools and humans is complete. As Mike joked, the Hubble commercial might go like this: EVA Set-up — 3 hours. Pull and replace failed electronic cards — 15 minutes. Resurrect Science — Priceless.

Here’s Mike Massimino practicing with the mini-power tool working on a test article.

I just love getting questions like this one that help us all think about the science and engineering marvels we’re creating today. I only wish I could start my career all over again and see what the next 30 years bring.

Colleen

Ground Support Personnel Practice for Last Mission to Hubble

Introduction

I am the HST Development Project Scientist, responsible for ensuring all new hardware developed for SM4 meets its scientific goals. I am also the Instrument Scientist for the Wide Field Camera 3. The HST Project developed this facility instrument on behalf of the astronomical community and as such has no principal investigator. We have a local science team that is responsible for dealing with day-to-day issues related to the instrument’s scientific performance and for carrying out its ground calibration. In addition, an external Science Oversight Committee, chaired by Prof. Robert O’Connell of the University of Virginia, represents the broader community and provides overall guidance regarding scientific matters. I have a BS in Physics from the Massachusetts Institute of Technology, Cambridge, and a Master’s and Ph.D from the University of California, Berkeley also in Physics.

21 August 2008

9:00PM.     Just arrived at Johnson Space Center for the Servicing Mission 4 JIS (Joint Integrated Simulation) #5 – “Joint” because it is supported by both Johnson, lead center for space shuttle on-orbit operations, and Goddard, lead center for HST (Hubble Space Telescope) operations. Just as the astronauts must practice repeatedly for the mission, so must the ground support personnel. The mission is short, and the time during the 5 scheduled spacewalks is particularly precious. It is therefore necessary for experts on all shuttle and HST systems and procedures to be on console to address any problems as they arise – with round-the-clock operations, there ends up being hundreds of people who support the mission.

My station is in the Blue Flight Control Room (FCR), or as we call it, the “blue ficker”, at JSC with some other HST personnel (more HST personnel are stationed back at Goddard). Shuttle ops are controlled from the White Flight Control Room down the hall. Upstairs is another large room with many other HST support personnel monitoring various hardware subsystems. Also upstairs in this same building is the old Apollo control room – “Tranquility Base here, the Eagle has landed…”, “Houston, we have a problem…” – a goose-bump-raising site that we have all visited when not on duty.

From left, Randy Kimble, David Leckrone, Preston Burch (all from GSFC), Matt Mountain (STScI), Mike Kienlen and Keith Kalinowski (both from GSFC) at a management console during the joint integrated simulation at JSC on Aug. 21.

As Instrument Scientist for the new Wide Field Camera 3 (WFC3), I am particularly eager tonight to see how the functional test of the newly installed instrument goes (the Simulation, or “sim”, picked up this evening a few hours after the astronaut installation of WFC3 on the first EVA – Extravehicular Activity – day). WFC3 has two observing channels – the ultraviolet/visible (UVIS) channel can be checked out pretty well, even though the Charge-Coupled Devices (CCDs) will not be fully cooled until several weeks after release of the telescope; for the infrared (IR) channel, we can check out the electronics, but the detector is much too warm during the Servicing Mission to yield any actual imaging data.

22 August 2008

3:00AM.     Success! WFC3 has passed its functional test! Both channels look completely nominal. There is one small telemetry issue – looks like a bad readout on a temperature sensor – but nothing that should impair operations. A good feeling in Sim land, and we’re all hoping for the ecstatic feeling of equivalent success in the real servicing mission functional test that should be happening a mere seven weeks from now!

The main issue for the rest of the night will be some forward planning of the upcoming EVAs – there is a simulated problem with the rotator that orients HST properly so that the work site to be serviced faces the crew cabin; this means that the telescope will have to be manually rotated at the beginning and end of each day’s EVA at the cost of a significant amount of EVA time. We’ll have to give up something in the planned timeline for each day, so there is a lot of discussion of the various options, based on the priorities that have been set for the various mission elements (the new hardware and the STIS – Space Telescope Imaging Spectrograph – and ACS – Advanced Camera for Surveys – repair tasks) and the logistics of how things pack into a given day’s activity. It appears that it will basically come down to a choice between repairing ACS and installing a new Fine Guidance Sensor. Sad to lose one, but most of the mission content can be retained.