**TOWARDS A SOFIA UPPER DECK RESEARCH FACILITY**

Peter Jenniskens^1^, Hansjuerg Jost^2^, Ray W. Russell^3^, Mike J.
Taylor^4^, Tim Castellano^5^,

Hans C. Stenbaek-Nielsen^6^, Frans J.M. Rietmeijer^7^

^1^*The SETI Institute, 2035 Landings Drive, Mountain View, CA 94043,
USA*

^2^*The BAER Institute, Mountain View, CA 94043, USA*

^3^*The Aerospace Corporation, Los Angelos, CA, USA*

^4^*Utah State University, Logan, UT, USA*

^5^*NASA Ames Research Center, Moffett Field, CA, USA*

^6^*University of Alaska, Fairbanks, AK, USA*

^7^*University of New Mexico Albuquerque, NM, USA*

**ABSTRACT**

The Stratospheric Observatory for Infrared Astronomy (SOFIA), an
airborne infrared and submm observatory, will deploy on 8 hour nights a
rate of 960 flight hours per year for 20 years once it is operational.
During those flights, it will execute a rigorous observing program in
astronomy. Serendipitous research is possible from the Upper Deck of the
B747 aircraft, offering a window on the aircraft environment and into
space from nine not yet occupied windows. In this paper, we briefly
review some of the science questions that can be uniquely addressed from
SOFIA with modest instrumentation. This will serve as a basis for
further discussion during the 2004 SOFIA Upper Deck Enbabled Science
workshop at NASA Ames Research Center.

**INTRODUCTION**

SOFIA is the Stratospheric Observatory for Infrared Astronomy - a world
class astronomical observatory for infrared and submm astronomy. It is
an airborne observatory with projected flight hours as much as 960
hours/year (8 hour nights) for 20 years.

The Upper Deck of the USRI operated B747 SOFIA may in the future
facilitate experiments for serendipitous research during regular
deployments, or in support of ongoing mid-IR and submm observations with
the main telescope. Preferentially, this research will support NASA\'s
and DLR\'s mission goals.

The SOFIA Upper Deck may, for example, facilitate some of the same
instruments as currently

developed for the NSF/NCAR HIAPER aircraft, which unlike SOFIA has short
dedicated missions with a focus on specific atmospheric processes.

Serendipitous research on SOFIA should exploit the capability for
long-term monitoring at altitude. In addition, short-term programs could
benefit from the low extinction near the horizon (higher meteor rates),
a better scintillation than on the ground (occultation observations), a
much lower water vapor absorption (near-IR and mid-IR spectroscopy and
photometry), a high cosmic ray background, and the unique ability to
provide interactive experiments, for example for the

collection of interplanetary dust particles and aerosols in the
atmosphere.

Unique Earth Science research is possible due to frequent transitions of
the tropopause.

There are also unique opportunities for education and public outreach,
by facilitating student experiments, providing in-cabin video, and for
sightings of transient phenomena on the sky (elves, aurora, fireballs).

No decision has yet been made to support such use of the Upper Deck at
the present time. Better insight is needed into the most effective use
of the facility and the requirements for those efforts not to interfere
in any way with the operations of the astronomical observatory. This
information will be used to work towards creating a multi-user facility
that can accomodate existing instruments, well shielded from the rest of
the aircraft.

![](media/image1.png){width="4.2in" height="1.820138888888889in"}

Fig.1. SOFIA\'s Upper Deck and placement of the Water Vapor Monitor, in
an engineering drawing published on the DLR Sofia website. The partition
is currently not being planned.

**THE SOFIA UPPER DECK**

There are 10 windows tilted at 27.8 degrees upward, which permit viewing
±40 degrees in azimuth and between 0 - 68 degrees in elevation, if
equipped with the right window materials. This includes any position on
the sky that can be reached by the SOFIA telescope. One observatory
facility instrument (a water vapor monitor) has been installed
permanently on the Upper Deck on the one before last window on the left
hand side facing the cockpit,creating a presedent for other
installations. The back of the upper deck also houses vacuum pumps that
will pump on science instrument cryostat vacuum enclosures. There is
easy access from the forward cabin, a large empty space, and ample
power, while any weight acts as counter weight to balance the telescope.

![](media/image2.png){width="3.5in" height="2.0930555555555554in"}

Fig.2. The Water Vapor Monitor and its placement on the Upper Deck.
Drawing and image courtesy Tom Roellig, NASA Ames Research Center.

A critical part of SOFIA\'s operations is the Water Vapor Monitor of
which Tom Roellig of NASA Ames Research Center is the Prinicipal
Investigator.

The Water Vapor Monitor measures the water vapor content of the
atmosphere integrated along the line-of-sight at a 40 degree elevation
angle by making submm radiometric measurements of the center and wings
of the 183.3 GHz rotational line of water. These measurements are then
converted to the integrated water vapor along the telescope
line-of-sight.

The monitor hardware consists of three physically distinct
sub-systems: 1) a 12 lbs. radiometer head mounted in a pressure vessel,
2) an IF Converter Box Assembly, and 3) an operating computer, which are
mounted in a cabinet just under the radiometer head. The window plug
contains a 5\" size 0.15 inch thick stretched acrylic window suitable
for optical observations.

The Water Vapor Monitor is powered on 15 VDC at 1.5 amps maximum, but
taps power from a supply of 110V/60Hz. A flow of dry air is collected
from the air ducts that keeps the windows free of frost.

This is a FAA approved setup that can be copied to accommodate other
instruments.

**POTENTIAL SOFIA UPPER DECK ENABLED SCIENCE IN ASTRONOMY**

SOFIA\'s high cruising altitude will enable astronomical observations
above 75 percent of the atmosphere, above nearly all of the water vapor
column, and with a cloud-less low-extinction view on the horizon. This
provides low scintillation for occultation studies, low absorption in
the water vapor bands for near-IR, mid-IR, and submm observations, and
4 - 5 times higher meteor rates than are seen from the ground.
Observations from the Upper Deck on SOFIA could help answer key science
questions and issues as defined in the NASA Space Science roadmaps.

*Space Science Fundamental Questions:*

-   How does life begin and evolve?

-   Where do we come from? Where are we going?

-   How does the Earth respond to solar interactions with the Earth\'s
    atmosphere and space environment.

-   What are the impacts for humanity from space weather, changes of
    Earth\'s atmosphere, habitability of space.

Potential contributions of measurements based on the SOFIA Upper Deck:

-   Determine any chemical precursors of life from exogenous delivered
    organics

-   Support of regular SOFIA observatory program for relatively bright
    objects such as comets and gamma-ray bursts

-   Learn how the Sun\'s family of planets and minor bodies originated
    from the compositional diversity of comets and asteroids

-   Understand how the solar system evolved to its current diverse state
    from the search for extrasolar planets

-   Characterize the cosmic and endogenous sources of matter (organic
    and inorganic) for potentially habitable environments in a long-term
    collection of stratospheric dust

-   Explore the space environment to discover NEO hazards to Earth and
    meteor flux reporting during storms for satellite impact hazard
    mitigation

*Examples:*

*Search for extrasolar planets:* How frequent are planets? How large are
known asteroids? The lower scintilllation onboard SOFIA makes it
possible to perform occultation measurements at much higher precision
than from the ground. Not inhibited by clouds, observations may include
asteroid and kuiper belt occultations of distant stars, and perhaps even
gravity lenzing by brown dwarfs. SOFIA Upper Deck research could
contribute uniquely to survey-type observations of relatively bright
stars, where accurate photometry rather than sensitivity is important,
and could add to occultation capability with the main telescope by
providing observations at other wavelengths.

*Diversity of minor bodies:* How do comets and asteroids differ in
elemental and mineral composition? The rate of visible meteors per
square degree is nearly independent from elevation as seen from the
ground, but low extinction near the horizon causes rates to be 4-5 times
higher in airborne observations. The effect is stronger for brighter
fireballs. This enables the systematic study of meteoroid composition.
In comparisson, current high-resolution cooled CCD spectrographs provide
1 usefull psectrum per Perseid shower in ground-based observations, and
need 21 nights of sporadic observations for one spectrum. SOFIA: over 4
spectra per shower, less than 4 sporadic nights per spectrum. SOFIA also
makes it possible to observe with Moonlight and in cloudy weather.

*Interactive interplanetary dust collection:* SOFIA will fly high enough
to facilitate the collection of interplanetary dust particles and
aerosols. What is responsible for the frequent (seasonable, annual,
intra-annual) changes in collected interplanetary dust properties? The
interactive capability makes it possible to frequently exchange the
collection container for high temporal (and spatial) resolution of dust
grain collection.

*Wide field imaging support of SOFIA main facility:* The upper deck
could also facilitate wide field optical observations of comets during
SOFIA mid-IR and submm observations. Mid-IR observations of the sky
background can support the telescope operations by alerting the presence
of clouds (imaging) and variations in carbon-dioxyde absorption
(spectra).

**POTENTIAL SOFIA UPPER DECK ENABLED SCIENCE IN EARTH SCIENCES**

SOFIA will fly about 4 times a week about 8 hours. At the beginning,
these flights will mostly be out of Moffett Field, CA. Only after a few
years, deployments to the Southern Hemisphere are planned. SOFIA will
mostly sample the tropopause region of the Earth atmosphere at cruise
altitude, and initially many profiles in and out of Northern California.
This flight pattern is well suited for Earth Science research.
Observations from the Upper Deck on SOFIA could help answer key science
questions and issues as defined in the Earth Science Enterprise
Strategic Plan.

Earth Sciences Fundamental Questions:

-   How is the Earth changing and what are the consequences for life on
    Earth?

-   How is the global Earth system changing?

-   What are the primary causes of change in the Earth system?

-   How does the Earth system respond to natural and human-induced
    changes?

-   How will the Earth system change in the future?

Potential contributions of measurements based on the SOFIA Upper Deck to
the following programs:

-   the Global Water and Energy Cycle

-   the Carbon cycle

-   Atmospheric Chemistry

-   Aerosols

-   Weather and Short-Term Climate Forecasting

-   Long-Term climate Change

Beyond Earth Sciences, a SOFIA Upper Deck Research Facility could
contribute to the following questions as well:

-   Geodynamics and Other Solid Earth Activities

-   Astrobiology Fundamental Question \"What is the future of life on
    Earth and beyond?\"

-   Astrobiology Goal 6 - \"Understand the principles that will shape
    the future of life, both on Earth and beyond. Elucidate the drivers
    and effects of ecosystem change as a basis for projecting likely
    future changes on timescales ranging from decades to millions of
    years\"

-   Sun Earth Connections Roadmap Quest II - How do the Earth and
    planets respond? Solar interactions with the Earth\'s Atmosphere and
    Space Environment. Comparative Space Environment.\"

-   Sun Earth Connections Roadmap Quest III - \"What are the impacts for
    humanity? Space Weather, changes of Earth\'s atmosphere,
    habitability of Space\"

*Examples:*

*Elemental transport through the tropopause:* SOFIA will fly frequently
through the tropopause, with a cruizing altitude in the lower
stratosphere. The cross tropopause transport is not well understood.
What drives water vapor concentration in the stratosphere? What
chemistry occurs in the tropopause? What are the radiation properties
ofthin clouds and aerosols.

*Gas and aerosol collection:* Aerosol collection and gas sampling are
possible over long time baselines for studies of global climate change.
SOFIA gives the opportunity to monitor gasses at night time, important
for odd-nitrogen chemistry.

*Polar Mesospheric Clouds:* Polar mesospheric clouds (PMC), also known
as noctilucent clouds, are created by ice crystals in the mesoshere.
Observation from aircraft would allow the identification of PMC
structure over spatial scales not possible from the ground and not yet
done by spacecraft. By determining the variation in the clouds
brightness with viewing angle we can infer the size of the scattering
particles. The airborne observations will also add to the science
attempted through the NASA AIM satellite intended for a study of PMCs
and planned for launch in September 2006.

*Airglow and gravity waves:* Gravity wave structure in OH airglow can be
observed over long baselines and long timescales.

Other science objectives may well be achieved, the topic of discussion
at the first Workshop on future SOFIA Upper Deck enabled science (June
24-25, 2004) at NASA Ames Research Center.

Acknowledgements: We acknowledge support from NASA\'s APRA program and
NASA's Earth Science Enterprise to make this workshop possible.

**REFERENCES**

Chyba, C.F., P.J. Thomas, L. Brookshaw, and C. Sagan, Cometary Delivery
of Organic Molecules to the Early Earth. *Science,* **249**, 366-373,
1990.

Des Marais, D.J., L.J. Allamandola, S.A. Benner S.A., et al., The NASA
Astrobiology Roadmap. *Astrobiology* **3**, 219-235, 2003.

Jenniskens P., and R.W. Russell, The 2001 Leonid Multi-Instrument
Aircraft Campaign - an early review. ISAS-SP 15, 3-15, 2003.

Jenniskens P., Preface. Preface to special issue of COSPAR session on
"Meteor induced chemistry, ablation products, and dust in the middle and
upper atmosphere" (Houston, Oct. 2002). Advances of Space Research 33,
1443, 2004.

Rietmeijer, F.J.M., Interrelationships among meteoric metals, meteors,
interplanetary dust, micrometeorites, and meteorites. *Meteoritics
Planetary Science*, **35**, 1025-1041, 2000.

Russell, R.W., G.S. Rossano, M.A. Chatelain, D.K. Lynch, T.K.
Tessensohn, E. Abendroth, and D. Kim, Mid-Infrared spectroscopy of
persistent Leonid trains. *Earth, Moon and Planets,* **82-83**, 439-456,
2000.

Schmidt G., Astrobiology Target of Opportunity: The Leonid Storms.
*Astrobiology* **4**, 65-66, 2004.

Stenbaek-Nielsen,, H., and P. Jenniskens, Leonid at 1000 Frames per
Second. *ISAS-SP,* **16**, 207-214, 2003.

Taylor, S., J.H. Lever, and R.P. Harvey, Numbers, types, and
compositions of an unbiased collection of cosmic spherules. *Meteoritics
Plan. Sci.,* **35**, 651-666, 2000.

E-mail address of P. Jenniskens: <pjenniskens@mail.arc.nasa.gov>

Manuscript received 2004 February 08; revised 2004 May 09; accepted 2004
May 09.