Caltech EM27/SUN FTS

The EM27/SUN is an instrument commercailly avaliable from Bruker Optics(TM). Caltech owns one of these instruments which we have use in conjunction with TCCON instruments (e.g. the one at Caltech) to provide ground validation for and check for biases in OCO-2.   We also anticipating using this instrument to examine emissions of various gases from point locations and sources in the South Coast air Basin (SCB).

This project is currently (Aug 2016) worked on by graduate student Jacob Hedelius with some assistance from various other in the Carbon Cycle side and from collaborators at JPL. Former Caltech participants include Camille Viatte (who now primarily works with OCO-2 data, and still works with it on occasion).

An online e-notebook for this instrument is avaliable on the private TCCON-wiki page.


Resolution: 0.5 cm-1

Geometric distance moved: 0.45 cm

Optical path difference: 1.8 cm

Detector/Range: (standard) InGaAs ~550012000 cm-1

Gases measured: CO2, CH4, CO, H2O, N2O, O2


Projects Worked on

OCO-2 Validation

Because of the TCCON site at Caltech, Pasadena has frequently been targeted by OCO-2.  We have gone out several times (6+) to various places in Pasadena on OCO-2 targeted days.  In a single day we are able to make measurements at about 3 to 6 locations.  All of our equipment easily fits inside the back of a pickup truck.  Usually on these days we start and end by comparing with TCCON (see figure).

mobileFTS at Caltech.jpg

Measurements Around Emission Source (Chino CA dairies)

In January 2015 we hosted a mobile FTS campaign.  This campaign had 2 goals: 1) intercompare the mobile FT spectrometers and 2) measure emissions from a source in the SCB.  This campaign included participants from Caltech, JPL, LANL, and Harvard.  This was the first campaign of the mobile FT spectrometers in the U.S.  Overall we accomplished our goals, though every is working to provide the final versions of their data.  This campaign invovled work with 4 mobile FT spectrometers, 1 TCCON spectrometer, 2 picarro CRDS, and various meterological stations.

 This work has resulted in two publications:

Chen, J., Viatte, C., Hedelius, J. K., Jones, T., Franklin, J. E., Parker, H., Gottlieb, E. W., Wennberg, P. O., Dubey, M. K., and Wofsy, S. C.: Differential column measurements using compact solar-tracking spectrometers, Atmos. Chem. Phys., 16, 8479-8498, doi:10.5194/acp-16-8479-2016, 2016.

Viatte, C., Lauvaux, T., Hedelius, J. K., Parker, H., Chen, J., Jones, T., Franklin, J. E., Deng, A. J., Gaudet, B., Verhulst, K., Duren, R., Wunch, D., Roehl, C., Dubey, M. K., Wofsy, S., and Wennberg, P. O.: Methane emissions from dairies in the Los Angeles Basin, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-281, in review, 2016.


Cross comparisons with other EM27s

We have had visitors from Harvard, LANL, and JAXA bring their EM27/SUN instruments to compare with the Caltech EM27/SUN as well as the Caltech TCCON. This work has resulted in one publication and several conference presentations:

Hedelius, J. K., Viatte, C., Wunch, D., Roehl, C. M., Toon, G. C., Chen, J., Jones, T., Wofsy, S. C., Franklin, J. E., Parker, H., Dubey, M. K., and Wennberg, P. O.: Assessment of errors and biases in retrievals of XCO2, XCH4, XCO, and XN2O from a 0.5 cm–1 resolution solar-viewing spectrometer, Atmos. Meas. Tech., 9, 3527-3546, doi:10.5194/amt-9-3527-2016, 201.

Shiomi, K., Kuze, A., Kawakami, S., Katakoa, F., Hedelius, J., Viatte, C., Wennberg, P., Wunch, D., Roehl, C., Leifer, I.., Tanaka, T., Iraci, L., Bruegge, C., and Schwander, F.  GOSAT CO2 and CH4 validation activity with a portable FTS at Pasadena, Chino, and Railroad Valley. Poster presented at American Geophysical Union Fall Meeting, San Francisco, California; 14-18 December 2015, Abstract ID: A41I-0162.




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