Column Observatory

The first ground-based FTS observatory was assembled and tested at Caltech. It includes a high-resolution spectrometer, telescope dome, solar tracker, weather station, and camera.

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A home telescope dome (Technical Innovations, Inc.) is mounted on the roof. A Bruker suntracker is installed inside the dome.

A camera and weather station (pressure, temperature, relative humidity, wind speed, wind direction, pyranometer, presence of rain, and lightning detector) are also mounted on the roof.




Robodome Solar Tracker
Robodome containing solar tracker Bruker solar tracker



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The Bruker 125HR Fourier Transform Spectrometer has a 1.59 scanner path length, allowing a maximum resolution of 0.0063 cm-1.

This instrument is optomized for the near-infrared spectra region, with a CaF2 beamsplitter and gold-coated mirrors.



Two detectors simultaneously measure the solar spectrum:
InGaAs detector (3900 - 11000 cm-1)
Si diode detector (11000 - 15800 cm-1)

Using this instrument to record near-IR solar spectra, we measure CO2, CH4, CO N2O, H2O, HDO, HF, and O2 in the atmosphere.

Park Falls Tall Tower Research Site

In May 2004, the first Caltech FTS laboratory was shipped to the WLEF Tall Tower site in Park Falls, Wisconsin. The experiment is automated and can be monitored remotely. The WLEF Tall Tower is an interesting site because of the long-term monitoring already underway.


WLEF Tall Tower with FTS Laboratory


Collaborations at the WLEF Tall Tower Site:
The 447-m tall WLEF TV transmitter tower in northern Wisconsin became the second site for the NOAA CMDL Tall Tower program in October 1994. This tower is owned by the State of Wisconsin Educational Communications Board. Mixing ratios of CO2 are continuously monitored at 11, 30, 76, 122, 244 and 396 m above the ground. Wind speed, wind direction, temperature and relative humidity are measured at 30, 122 and 396 m. A weekly flask sampling program is also active at the site.

Scientific Results

Under clear sky conditions, 0.1% measurement precision is demonstrated for the retrieved column CO2 abundances. During the Intercontinental Chemical Transport Experiment-North America (INTEX-NA) and CO2 Boundary Layer Regional Airborne Experiment (COBRA) campaigns in summer 2004, the DC-8 and King Air aircraft recorded eight in situ CO2 profiles over the WLEF site. Comparison of the integrated aircraft profiles and CO2 column abundances shows a small bias (2%) but an excellent correlation.

Complete details about the initial scientific results can be found here.