Who's Sitting in the Driving Seat when you Fly the Infrared Friendly Skies?
Posted on May 23, 2013 06:49:59 PM | Kimberly Ennico
Note: The pictures in this blog are taken from a recent line operations (when SOFIA is not in flight, but being operated on the runway) on May 23, 2013. As the program is in its iterative operations phase, these pictures capture the inside of SOFIA on this date. There will be additional preparations to enable the required safe readiness for the flights, the first set for May 30th.
At one level SOFIA is quite simple: you want to point the telescope at for target, hold there on the instrument sensor array for a set amount of time, maybe repeat the observation to allow for better signal-to-noise, and then move on to the next target. At another level, SOFIA is quite complicated as you have a moving observatory (in several degrees of freedom, i.e., forward, left, right) that is trying to target, "peak up" and stay on target for several minutes by which the observatory and/or the target has moved enough.
Mission Director: He/she is responsible for ensuring the flight meets the success criteria and is safe. They run the readiness reviews and summary the milestones for the flight campaigns. They also make decisions if needed to deviate from plan. They keep track of how well we are executing the plan.
The Flight Planner: On the plane he/she sits next to the Mission Director. Lots of work is done ahead of the actual flights to map out an optimized series of “flight legs” to maximize the time spent on target. As the telescope has a fixed position within the aircraft (aft-port), a leg towards the West (in the Northern Hemisphere) means the sky target is in the south; a leg towards the North means the sky target is in the west, etc. When SOFIA flies in the Southern Hemisphere, this gets reversed.
More information about SOFIA Flight Legs can be
SOFIA Flight Plans
The Telescope Operators. Sitting close to the telescope, they monitor the telescope set-up and operations and real-time interfaces with the science instrument. Each science instrument will have different requests for the telescope assembly. They also perform the Line Of Sight rewinds periodically. Normally this is scoped out in advance but this is envisioned to be a manual operation performed with agreement the Instrument Scientist’s okay. For example, you don’t want to interrupted an observation, so you are watching the clock and the angles in real time to know when this activity is needed.
More information about SOFIA Line of Sight can be
SOFIA Line Of Sight Rewind
Instrument Scientist. Each science team will have an Instrument Scientist who knows the “ins and out” of the instrument and the subtleties of changes to observations or techniques. He/she is in constant communication with the Telescope Operator as well as the Principal Investigator of the observations. Science Instrument observations are run mainly by pre-written and pre-tested scripts, but sometimes there are some manual observations that the Instrument Scientist can execute.
There is also a lead for the MCCS, the Mission Controls and Communication System, to supervise the performance of that critical subsystem. This software controls the communication between the science instrument and telescope as well as all the archiving of any data taken during the line ops or flight.
There is the Science Team who is on board for the in-real-time data reduction and assessment, in case an observation needs to be redone again or done differently, a principal investigator who decides the priorities of the science observations for the flight and directs the science team and two pilots and a flight engineer for flying the aircraft.
Finally, there is space allocated for ride-along teachers and other guests who can participate in SOFIA science.
To learn more about the SOFIA Airborne Ambassador program check out SOFIA Airborne Ambassadors Program
'To Chop, Nod, or not Chop, Nod. That is the question.' SOFIA FORCAST May 23, 2013, line-ops.
Posted on May 23, 2013 06:10:31 PM | Kimberly Ennico
I am out here in Palmdale, CA, not for a SOFIA flight (yes I
know that's where most people's interest peaks) but for a critical step called
line-ops, or operations on the flight line. Essentially we are going through
exactly what we plan to while the plane is at altitude and work on end-to-end
data testing, assessing observation timing, and communication, both among the
different people needed to complete the observation and also between we humans
and the highly complex software subsystems.
At 2130h May 22, crew briefing. We covered the main
readiness topics: Weather (winds, humidity), Required Personnel, Aircraft
Status and Configuration (System Engineer reported out), Telescope Status,
Mission Systems Status (Flight Systems reported out), Operational Timeline
(roll out, people on, telescope door open, telescope door closed, people off,
roll back to hangar), Mission Rules (don’t connect laptops to the internal
system and wireless at same time, bring drinks in closed containers, get
permission before entering roped off areas, etc.), Safety & Emergency
Procedures (exit doorway locations, footwear required), and Test Summary.
Being on SOFIA is not like flying on a normal 747 jet. I
hope from the various photos in this blog entry and others, you’ll see it’s got
“other things” like computer racks, a whole data collection and archiving
server farm on board (the MCCS), conference tables, and various electrical
panels needing access for maintenance or operation. It’s got airline seats
(with the normal seatbelts) for takeoff and landing and places to store your laptop
bags, but the similarities end there.
So last night we got through some key tests. We did a pupil
check (to optimize alignment of the FORCAST instrument to the telescope). Next
were a series of inspections of the telescope boresight (telescope centered on
a star) and how that appeared on all the imaging (all filters) and spectroscopy
(for all grism and slit combinations) modes. We learned we had a systematic
offset in our slits, but we updated the .ini file to address this. Then we did
some testing of the basic modes. We tested chop-nod-dither in the SIRF and ERF
coordinates. SIRF=Science Instrument Reference Frame (rows & columns on the
detector array). ERF=Equatorial Reference Frame (RA/DEC on the sky). There is
also a third coordinate system, the TARF=Telescope Assembly Reference Frame (elevation,x-elevation
angles). Yes, astronomers love their coordinate systems.
Below is a photo of one of the chop-nod tests, on a bright target
star. It’s chop-nod-match mode. Left is the Science Instrument Console with
quick look software showing a reduced subtracted image (you see the positive
and negative star images). The right image shows a series of display for the
telescope guide camera and telescope display.
With the remaining hours for this night, we started probing
the space of the chopping throw vs. angle. Below is an example of a large chop
that was bumping up against a hardstop of the secondary, so we spent the rest
of the night investigating that issue. The scale bar on the lower left of that
guide star camera image is 1 arc minute.
The telescope door was closed at 0500h. Sunrise was at
0545h. We’ll regroup later tonight to address the series of tests for tonight.
There will be a crew briefing at 2130h to assess readiness for tonight.
Oh, surprise to me, we had internet on lineops, so
I was tweeting away in near-real time we did our testing and I also got some
IDL coding done for the pipeline end-2-end tests.
Stairway to the stars. Climbing aboard the SOFIA Airborne Telescope
Posted on May 23, 2013 12:57:30 AM | Kimberly Ennico
We got the “go” to proceed with line ops. SOFIA, a 747SP,
was towed out of its hangar onto a side-runway, and away from any air traffic. The
heading is 130.5. This is important as it tells us what view angles are
available from the telescope. The telescope looks out the aft-port side of the
aircraft. (Aft=back of wing, Port=left side, when viewed from the back, facing
the front). So at this heading, we are looking at the N-E portion of the sky.
Our calibration targets include TDra, NSV25184, RUCyg, muCep, and TCass, all
pretty bright stars.
We walked out from the hangar to the craft and can come/go
from the craft during the night. Of course, this is not what will be like
during the flight. Below is a picture of our ingress/egress path on the plane,
a “true stairway to the stars.”
I learned that for the flights, we would do a similar activity, meaning we do
not board within the hangar, but board after the craft has been towed out to
Using the waiting time wisely to make the best use of the remaining ops ahead.
Posted on May 22, 2013 11:54:51 AM | Kimberly Ennico
Line ops last night were cancelled due to a “no-go” by the
telescope assembly subsystem. A problem had been found that could not enable
observations tonight. It was a call the science team did not want to hear, but
it was the right call. This exercised the reason why there is a “readiness
review” before going out to execute a complex activity. A plan was put in place
for the 1st shift when they get in at 7am (0700h) today (Wed) to address the
problem and report back during the day. If all goes well, a crew-briefing will
be scheduled again at 2130h tonight and we can resume lineops at 2300h.
If we were observing using a ground-based telescope, we
watch the weather. A seasoned ground-based observer watches the humidity. You
can often get obsessed looking at trends in pressure, temperature, etc. It’s
important as you may need to replan your allotted observation time if you lose
a night (or nights) to the weather-gods.
When I assisted with a balloon launch last summer at Ft. Sumner, NM, we’d
gather daily to address the winds. Winds were most stable at dawn so we’d have
our “crew briefing” at 3 or 4am with readiness to roll out at 5am with the hope
to launch in the next hour or so (it would take nearly an hour to do the roll-out
of the balloon and the He fill). Yes, sometimes the call would be made at 3am
for a “no-go” or even as late as right before the fill. And then you roll back
the 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 in
the schedule, two this week and one contingency night next week, which now
seems to be required. Also, we’ve started looking at the flights scheduled for
next week, to see what tests planned in flight would supersede the line ops
tests to allow to compress our “line ops” schedule. Now, this is a calculated
risk since the purpose of line ops is to test the system end-to-end before
flight. So essentially you want to run the key components you plan to test in
flight on the ground first.
What are line ops anyway? It’s not as “dramatic” as the
actual flight, but it serves very important purposes to follow our observation
plan end-to-end, address timing issues, and most importantly, communication between
people and communication between people & machines. The plane is towed out
on the runway to a viewing position safe from any active runway traffic, and
preferably 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 start
running through a series of discrete tests, some of which are to be run exactly
on the flights, and other diagnostic tests that are needed that would otherwise
take up the valuable flight time.
One of the tests we want to do is test the “nod” function of
the telescope and how the data sets we collect affect our observing strategy
optimization (ahem, improve signal to noise). In mid-IR astronomy, the sky
background is “brighter” than our targets. In fact, we often cannot see our
targets in the original raw data until we do a “background subtraction.” So we
use the telescope’s secondary mirror to “chop” a source back & forth (as it
would appear on our detector) at a fast rate. And then we would command the
telescope 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”
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 to
your science target which can be anywhere in the sky, we’d like to understand
the system performance and, if any, limitations.
We have other tests planned like assessing the detector bias
performance, looking at flexure of our alignment, particular for our grism mode
where we have narrow slits, optimizing a new flat field technique, and running
through the science scripts to checking for timing and fix any commanding
So fingers crossed, we will get on sky tonight, on the tarmac
at Palmdale, CA. The skies have been clear the last two nights, so we the
weather gods have been kind. We now need the electrical-power-subsystem gods to
Science enabled by the platforms of Air & Space
Posted on May 21, 2013 12:59:44 PM | Kimberly Ennico
I’m out here at NASA Dryden’s Aircraft Operations Facility,
the DAOF, to support line operations for the Stratospheric Observatory for
Infrared Astronomy, SOFIA. I’m normally a spacecraft science instrument
builder, having previously tested detectors for astronomy space telescopes Spitzer
and JWST and building, testing and operating a 10 instrument payload for LCROSS
that impacted the moon in 2009 detecting water within a permanently shadowed
crater. And since 2011, I am working instrument calibration operations for the
en-flight probe to Pluto, New Horizons.
Thus, SOFIA, being an aircraft, is a very different experience
for me, coming from the spacecraft side of the house.
Sitting in the DAOF with SOFIA are some of the world’s
premiere aircraft used for Earth Science observations, measuring in-situ
molecules in our planet’s atmosphere, capitalizing on a mobile platform that
can go monitor fires, or survey ice sheets at the poles, or observe transient
phenomena like meteor showers or spacecraft or space-sample return capsules.
Check out this amazing suite of aircraft and their
objectives at NASA’s Airborne Science Program:
NASA's Airborne Science Program
Tonight we roll out ~8pm local time for first night of line
ops from the 11pm-5am shift. I’m very eager to experience this important prep-activity
for SOFIA commissioning science flights which start next week.
More information about SOFIA's unique science can be found at NASA SOFIA Web Page
Posted on May 21, 2013 03:32:40 AM | Kimberly Ennico
Tonight’s line operations were cancelled due to open issues
recertifying work on reworked parts of the telescope assembly (TA) power
subsystem. There are no show-stoppers, just the need for more time for testing
and integration. Progress continues to be made. The cautious step was to make
the decision to start line ops tomorrow, and there is a contingency day next
week to make up time if needed. The schedule for the remaining three nights of
line ops will remain tight, but there is a plan. Creative re-ordering of tasks
will be the “philosophy” these next three days. Having worked operations on two
space missions, I can say that operations of any craft, air or space, is a
skill of “firm flexibility.”
This evening, I experienced a Technical Readiness Review
(TRR). This consisted of getting all the leads around a table and walking
through the status of each subsystem, who is needed where and when, what types
of testing will be done during the next few days, and when the daily crew
briefings will be held. Also addressed were questions posed by the visiting
science team to the operations team, to fill in some gaps. Today was the first
time the group had re-assembled since the last line & flight ops, which for
the FORCAST instrument, had been back in March. Since then, two other
instruments (HIPO/FLITECAM and GREAT) had been installed, tested, and removed,
and there have been software upgrades to both the telescope and telescope to
science instrument communications. This phase of operations is pretty complex,
folding in highly dynamic items that may seem be changing a lot, but it’s
actually normal. And the job of operations is to keep to schedule while still
achieving the tasks. Sometimes the path is different from the exact original
concept, but if the goals are met, it was a successful journey. At tomorrow’s
crew briefing at 2130h, open items from today’s TRR will be addressed and
closed before line ops begins, set for 2300h-0500h.
I’m still a bit on the sidelines, watching and learning from
the experienced SOFIA observers who have worked with SOFIA operations before.
During a lull this afternoon, I got a glimpse into the AORs, or Astronomical
Observation Requests, which is how an end-user communicates her requests to
enable an observing plan via scripted observational tasks. The AORs for our
upcoming lineops have been written, and one of my roles will be quick look data
analysis 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 the
inside (compared to what I had expected, that is.).
Being in the presence of a cool lady, a 747SP named the Clipper Lindbergh
Posted on May 20, 2013 04:04:25 PM | Kimberly Ennico
I have arrived here in Palmdale, CA. This is a new place for
me, so it has a share of expectations. Palmdale, just 50 miles north-east-ish
of Los Angeles is home to the Dryden Aircraft Operations Facility or DAOF, for
short. Upon arrival, I learned that NASA
Dryden Flight Research Center itself is about another 40 minute drive away, so
time permitting, I'd like to check out that sister center.
I've rendezvoused with two colleagues from Cornell and
Ithaca College who have both flown on SOFIA and also have put in so many hours
to make the FORCAST instrument a success. They are eager to get back to
operations & science observations again.
I've also met two graduate students, one who has flown already and
another, just as green-as-me, this being his first time to Palmdale and
checking out the *Stratospheric Observatory for Infrared Astronomy* for
Today marks a special
occasion for me to see SOFIA in all her shiny-white-paint with an organized crew
getting her ready for this week of line operations, or line ops. The reality is
intense. One can read about things on the internet or in papers, but to
actually 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.
instrument FORCAST, a mid-infrared instrument, is already installed and had its
latest cryogen fill this morning.
Tonight, line operations are scheduled from 11pm-5am and I
can 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.
747SP, the SP means “Special Performance.”