Using the waiting time wisely to make the best use of the remaining ops ahead.

Line ops last night were cancelled due to a “no-go” by thetelescope assembly subsystem. A problem had been found that could not enableobservations tonight. It was a call the science team did not want to hear, butit was the right call. This exercised the reason why there is a “readinessreview” before going out to execute a complex activity. A plan was put in placefor the 1st shift when they get in at 7am (0700h) today (Wed) to address theproblem and report back during the day. If all goes well, a crew-briefing willbe scheduled again at 2130h tonight and we can resume lineops at 2300h.

If we were observing using a ground-based telescope, wewatch the weather. A seasoned ground-based observer watches the humidity. Youcan often get obsessed looking at trends in pressure, temperature, etc. It’simportant as you may need to replan your allotted observation time if you losea night  (or nights) to the weather-gods.When I assisted with a balloon launch last summer at Ft. Sumner, NM, we’dgather daily to address the winds. Winds were most stable at dawn so we’d haveour “crew briefing” at 3 or 4am with readiness to roll out at 5am with the hopeto launch in the next hour or so (it would take nearly an hour to do the roll-outof the balloon and the He fill). Yes, sometimes the call would be made at 3amfor a “no-go” or even as late as right before the fill. And then you roll backthe balloon to the hangar. Last Sept, we launched on the 3rd attempt. All rocket launches also watch the weather and have various sub-system “go/no-go” checks.

SOFIA ops are not so different from those other examples.

So, we replan again. We have three remaining nights left inthe schedule, two this week and one contingency night next week, which nowseems to be required. Also, we’ve started looking at the flights scheduled fornext week, to see what tests planned in flight would supersede the line opstests to allow to compress our “line ops” schedule. Now, this is a calculatedrisk since the purpose of line ops is to test the system end-to-end beforeflight. So essentially you want to run the key components you plan to test inflight on the ground first.

What are line ops anyway? It’s not as “dramatic” as theactual flight, but it serves very important purposes to follow our observationplan end-to-end, address timing issues, and most importantly, communication betweenpeople and communication between people & machines. The plane is towed outon the runway to a viewing position safe from any active runway traffic, andpreferably in a location far from buildings or lights to obstruct viewing angles.We operate on plane-provided power. We command the telescope door to open,configure the telescope, check it out, power the science instrument, and startrunning through a series of discrete tests, some of which are to be run exactlyon the flights, and other diagnostic tests that are needed that would otherwisetake up the valuable flight time.

One of the tests we want to do is test the “nod” function ofthe telescope and how the data sets we collect affect our observing strategyoptimization (ahem, improve signal to noise). In mid-IR astronomy, the skybackground is “brighter” than our targets. In fact, we often cannot see ourtargets in the original raw data until we do a “background subtraction.” So weuse the telescope’s secondary mirror to “chop” a source back & forth (as itwould appear on our detector) at a fast rate. And then we would command thetelescope to “nod” to a different part of the sky. And repeat the process of“chopping” and “nodding” over a pre-planned orientation, both “throw distance”and “angle.”

You can read more about Chopping at Nodding at Why Chopping & Nodding is needed for SOFIA FORCAST Observations

An example taken from PDF on Signal to Noise Improvement by Chop/Nods sums it up nicely.

So we’ll be exercising things like this during the line ops,exploring the same technique for different roll angles because when it comes toyour science target which can be anywhere in the sky, we’d like to understandthe system performance and, if any, limitations.

We have other tests planned like assessing the detector biasperformance, looking at flexure of our alignment, particular for our grism modewhere we have narrow slits, optimizing a new flat field technique, and runningthrough the science scripts to checking for timing and fix any commandingerrors.

So fingers crossed, we will get on sky tonight, on the tarmacat Palmdale, CA. The skies have been clear the last two nights, so we theweather gods have been kind. We now need the electrical-power-subsystem gods tobe kind.

Science enabled by the platforms of Air & Space

I’m out here at NASA Dryden’s Aircraft Operations Facility,the DAOF, to support line operations for the Stratospheric Observatory forInfrared Astronomy, SOFIA. I’m normally a spacecraft science instrumentbuilder, having previously tested detectors for astronomy space telescopes Spitzerand JWST and building, testing and operating a 10 instrument payload for LCROSSthat impacted the moon in 2009 detecting water within a permanently shadowedcrater. And since 2011, I am working instrument calibration operations for theen-flight probe to Pluto, New Horizons.

Thus, SOFIA, being an aircraft, is a very different experiencefor me, coming from the spacecraft side of the house.

Sitting in the DAOF with SOFIA are some of the world’spremiere aircraft used for Earth Science observations, measuring in-situmolecules in our planet’s atmosphere, capitalizing on a mobile platform thatcan go monitor fires, or survey ice sheets at the poles, or observe transientphenomena like meteor showers or spacecraft or space-sample return capsules.

Check out this amazing suite of aircraft and theirobjectives at NASA’s Airborne Science Program:

NASA’s Airborne Science Program

Tonight we roll out ~8pm local time for first night of lineops from the 11pm-5am shift. I’m very eager to experience this important prep-activityfor SOFIA commissioning science flights which start next week.

More information about SOFIA's unique science can be found at NASA SOFIA Web Page

Firm Flexibility

Tonight’s line operations were cancelled due to open issuesrecertifying work on reworked parts of the telescope assembly (TA) powersubsystem. There are no show-stoppers, just the need for more time for testingand integration. Progress continues to be made. The cautious step was to makethe decision to start line ops tomorrow, and there is a contingency day nextweek to make up time if needed. The schedule for the remaining three nights ofline ops will remain tight, but there is a plan. Creative re-ordering of taskswill be the “philosophy” these next three days. Having worked operations on twospace missions, I can say that operations of any craft, air or space, is askill of “firm flexibility.”

This evening, I experienced a Technical Readiness Review(TRR). This consisted of getting all the leads around a table and walkingthrough the status of each subsystem, who is needed where and when, what typesof testing will be done during the next few days, and when the daily crewbriefings will be held. Also addressed were questions posed by the visitingscience team to the operations team, to fill in some gaps. Today was the firsttime the group had re-assembled since the last line & flight ops, which forthe FORCAST instrument, had been back in March. Since then, two otherinstruments (HIPO/FLITECAM and GREAT) had been installed, tested, and removed,and there have been software upgrades to both the telescope and telescope toscience instrument communications. This phase of operations is pretty complex,folding in highly dynamic items that may seem be changing a lot, but it’sactually normal. And the job of operations is to keep to schedule while stillachieving the tasks. Sometimes the path is different from the exact originalconcept, but if the goals are met, it was a successful journey. At tomorrow’screw briefing at 2130h, open items from today’s TRR will be addressed andclosed before line ops begins, set for 2300h-0500h.

I’m still a bit on the sidelines, watching and learning fromthe experienced SOFIA observers who have worked with SOFIA operations before.During a lull this afternoon, I got a glimpse into the AORs, or AstronomicalObservation Requests, which is how an end-user communicates her requests toenable an observing plan via scripted observational tasks. The AORs for ourupcoming lineops have been written, and one of my roles will be quick look dataanalysis to confirm they executed as expected. My colleague Luke Keller, from Ithaca College, is shown below crafting some new slit-stepping observations.

Oh, I got to step inside SOFIA today. She’s bigger on theinside (compared to what I had expected, that is.).

Being in the presence of a cool lady, a 747SP named the Clipper Lindbergh

I have arrived here in Palmdale, CA. This is a new place forme, so it has a share of expectations. Palmdale, just 50 miles north-east-ishof Los Angeles is home to the Dryden Aircraft Operations Facility or DAOF, forshort.  Upon arrival, I learned that NASADryden Flight Research Center itself is about another 40 minute drive away, sotime permitting, I’d like to check out that sister center.

I’ve rendezvoused with two colleagues from Cornell andIthaca College who have both flown on SOFIA and also have put in so many hoursto make the FORCAST instrument a success. They are eager to get back tooperations & science observations again. I’ve also met two graduate students, one who has flown already andanother, just as green-as-me, this being his first time to Palmdale andchecking out the *Stratospheric Observatory for Infrared Astronomy* forhimself.

 Today marks a specialoccasion for me to see SOFIA in all her shiny-white-paint with an organized crewgetting her ready for this week of line operations, or line ops. The reality isintense. One can read about things on the internet or in papers, but toactually see the physical metal,glimpse at her sleek curves, observe the crews keeping her safe and airworthy,is something else. And that’s just the outside.

The scienceinstrument FORCAST, a mid-infrared instrument, is already installed and had itslatest cryogen fill this morning.

Tonight, line operations are scheduled from 11pm-5am and Ican share what I learn.  Until then,pieces of the complex set of what goes into operating a facility such as SOFIA,are slowly coming into place.

For now, I just cannot help staring at this amazing beauty.

SOFIA at the Dryden Aircraft Operations Facility getting ready for a weight and balance test

747SP, the SP means “Special Performance.”