N° 5–1996: ERS-2 will track down the origins of ozone depletion

At a press conference today at its Space Technology Centre ESA-ESTEC in the Netherlands, the European Space Agency presented the first scientifically meaningful results derived from the Global Ozone Monitoring Experiment (GOME) onboard its ERS-2 satellite. "Whilst we have been observing the ozone hole from space for nearly ten years, it is now finally possible to measure on a global scale not only ozone values but the trace gases that make them fluctuate" said Professor Paul Crutzen, Director of the Max-Planck-Institut for Chemistry in Mainz and a winner of the 1995 Chemistry Nobel Prize, "a group of researchers has already seen in ERS- 2 spectra one of the most hunted after species namely bromine oxide. In the last fortnight, another group has succeeded in detecting chlorine dioxide".

ERS-2 was launched on 21 April 1995 and is now operating in tandem with its sister spacecraft ERS-1, launched four years earlier. A major improvement of ERS-2 over its predecessor is the addition of the GOME instruments, which over the past eight months has undergone a major calibration and validation campaign. "The algorithms to extract precise total ozone column values and other trace gases need to be fine-tuned and optimised. ERS-2 is just beginning to provide valuable ozone monitoring of a quality similar to that of US satellites. However, there is a lot of new science in GOME data. Its unprecedented spectral coverage will enormously expand our knowledge about atmospheric chemistry. Even with ten times more people and computers in my lab, I couldn't exhaust GOME's scientific potential. And this research matters" said Professor John Burrows of the University of Bremen, a leading GOME scientist.

As ERS-2 circles the Earth, the GOME instrument measures the intensity of "Earthshine" light over a large spectral range, at high resolution. "We have been used to 6 to 12 spectral channels. GOME provides 3500 channels providing scientists with a very powerful tool to observe many of the rare atmospheric species" said Christopher Readings, Head of ESA's Earth Sciences Division. "These trace gases are measured in parts per billion or even parts per trillion, and previously could only be measured from stratospheric balloons. ERS-2 measures on a global scale, 365 days a year. And it will be followed by Envisat with even better instruments".

ERS-2 transmits GOME data to two ESA ground stations in Kiruna in northern Sweden and in Gatineau in Canada, from where they are transmitted to the GOME data centre run by the German Aerospace Establishment, DLR. Here, the data is pre-processed and standard data products generated. About a dozen of scientists all over the world have been supplied with uncalibrated GOME data during the commissioning phase to help ESA with the validation of the system. "Collaboration between ESA and NASA is extremely beneficial to both sides, since it combines the long experience of NASA with SBUV and TOMS data with the powerful capabilities of the GOME instrument. We have been running NASA algorithms used for our Total Ozone Mapping System (TOMS) with GOME data. The results are great ant I am looking forward to a lot of exciting research, not just on ozone depletion but also pollution and the impact of volcanic eruptions on the atmosphere, to give just two examples" said Ernest Hilsenrath, Head of NASA's SSBUV Science Group.

GOME date will now become available to all research groups working in the field. In addition, DLR will regularly calculate global and European ozone maps for consultation by the public on the DLR World Wide Web server.

"By flying GOME in ERS-2, ESA helps us to safeguard the Earth's atmosphere", Professor Crutzen said. "The sooner we can replace chemical conjecture by precise measurements from space, the better our chances of minimizing man-made damage".