1. Balloon-Based Solar Occultation Spectrometry Using a
DA2 FTIR, and the PARABLE Project
Luke Collins1
, Alex Geddes2
, Pierre F. Fogal2
, Kaley A. Walker2
1
University of Waterloo, 2
University of Toronto
Introduction - What is Balloon-Based Atmospheric Spectroscopy?
Trace gases which contribute to the depletion of the global ozone layer, such as
nitrogen oxide compounds, are often of primary interest in studies relating to
stratospheric chemistry; balloon-based spectroscopic measurements have been
integral to such studies since the 1970s. Data from balloon-based instruments can be
acquired continuously over a relatively large local geographical area and can be used
as a comparison dataset for both ground-based and satellite spectral measurements.
PARABLE
Figure 1: CARMEN gondola with the PARABLE pay-
load; image provided by P. Vincent of the Canadian
Space Agency
The PAyload for Remote sounding of
the Atmosphere using Balloon Limb
Experiments (PARABLE) is one
example of a Canadian balloon project.
One of the goals of PARABLE is to
introduce graduate and undergraduate
students to the field of balloon-based
spectroscopy through:
I Development of remote communication
with a balloon borne payload
I Instrument interface development
I Data analysis and subsequent
comparison to satellite measurements
I Experience in field work
2015 Campaign
The PARABLE project launched a
payload consisting of four
spectrometers, two measuring in the
infrared range (DA2, PARIS), and two
in the ultraviolet-visible (SPS-B,
MAESTRO), for stratospheric trace gas
characterization. The approximately
20-hour flight was launched from
Timmins, Ontario, on September 13th
2015 by the Centre National d‘´Etudes
Spatiales (CNES) and the Canadian
Space Agency (CSA).
Figure 2: Above: Launch and descent details of the
2015 PARABLE flight. Below: Trajectory of the
balloon-borne payload.
Solar Occultation Method
Solar occultation is the process by which measurements through the atmosphere at
di↵erent heights above Earth’s surface are compared to an exoatmospheric
background to calculate transmission spectra for analysis. While balloon-based
measurements are inherently incapable of acquiring such a background, they can
measure above more than 95% of the atmospheric column. Balloon-borne data can
be used as a comparison dataset for validating satellite data sets.
I Spectral recordings occur at sunrise and sunset
I Analysis of discrete atmospheric layers uses ”layer-by-layer” algorithm[1]
Figure 3: Solar occultation demonstrated for ACE satellite measurements[3]
Fourier Transform Infrared Spectroscopy (FTIR)
Fourier Transform Spectroscopy (FTS) is the process by which raw data acquired
from a single radiative source can be converted into a power spectra through use
of Fourier Transforms. FTS enables simultaneous data collection over a wide
spectral range (multiplexing). Particular interest is given to the infrared region as
it contains many key vibration-rotation transition lines.
BOMEM BB-DA2 Fourier Transform Spectrometer
The Balloon-Borne Dynamical
Alignment System with a 2-inch
aperture (BB-DA2) is a Fourier
Transform Spectrometer who‘s design
is based on that of a Michelson
interferometer.
I First flown in 1977 with the University
of Denver
I KBr beamsplitter
I Dynamical alignment system allows for
stationary mirror correction to account
for instability in the moving mirror
I 50-cm maximum path di↵erence =)
unapodized Full Width at Half
Maximum (FWHM) resolution =
0.01cm 1
[2]
I Operates through solar occultation
I Detectors are cooled by liquid N2 and
are easily interchangeable
Figure 4: Top: Profiles from FTS Spectra of CH4,
N2O, O3, HNO3, HCl, CFC-11 and CFC-12/355
from the 1998 MANTRA Balloon Campaign[2]
Bottom: Table of observable species given current
detector configuration of DA2[4]
Recent Modifications to DA2
I Complete reconstruction of both
onboard and ground-based control
system software and associated
graphical user interface
I Heritage relay box used for onboard
instrument power control replaced
I New cables and connectors
I Primary instrument as well as
associated auxiliary devices have been
outfitted with new mounting plates Figure 5: BOMEM BB-DA2 FTIR[4]
References
[1] K. Strong et al. ”MANTRA - A Balloon Mission to Study the Odd-Nitrogen Budget of the
Stratosphere’”ATMOSPHERE-OCEAN 43. 4 (2005): 284-296. Print.
[2] P.F. Fogal et al. ”Infra-red FTS Measurements of CH4, N2O, O3, HNO3, HCl, CFC-11 and CFC-12
from the MANTRA Balloon Campaign”ATMOSPHERE-OCEAN 43. 4 (2005): 351-359. Print.
[3] K.A. Walker et al. ”Solar Occultation Measurements of Atmospheric Composition: SCISAT/ACE
and beyond” presented at: ATMOS 2012; 18 June 2012; Bruges, Belgium
[4] A. Geddes et al. ”Refurbishment of a DA2 FTIR for a Balloon Campaign” presented at:
NDACC-IRWG Meeting Toronto 2015; June 2015; Toronto, Canada
Acknowledgments
I This research was supported by Flights for the Advancement of Science and
Technology (FAST) grant program of the Canadian Space Agency (CSA).
I Thank you to Professor Kaley Walker and Dr. Pierre Fogal for providing me with
the opportunity to participate in the 2015 PARABLE field campaign.
Contact Information
I Email: l5collin@uwaterloo.ca
I Phone: +1 (519) 731 1817