CHEOPS (CHEmistry of Ozone in the Polar Stratosphere) was a series of research campaigns that involved the launch of stratospheric balloons carried out between 1987 and 1990 in the Arctic. The campaigns -whose objective was to study the problem of the ozone depletion in the region- were performed from the rocket launch range of ESRANGE, near Kiruna, Sweden, and involved several research institutions from France and Germany.

The first campaign CHEOPS I was conducted in Febraury 1987 when were performed two balloon launches. Although limited scientific results were achieved during this first attempt, it resulted in a growing interest of European scientists for developing and flying more powerful instrumentation.

Next year the International Ozone Trends Panel reported a systematic decrease of 6% of the total Ozone in the Arctic stratosphere in winter during a period between 1969 and 1986. This finding motivated several European researchgroups to continue the CHEOPS program by regular field campaigns organized in the Arctic region.

In 1988 during the CHEOPS II campaign four payloads were launched again from ESRANGE but this timne in cooperation with the balloon launching team of the French Centre National d'Etudes Spatiales (CNES). The experiments launched included a chemiluminiscent ozonometer, an IR polarimeter a whole cryogenic sampler and a ion mass-spectrometer. Also were performed measurements using a ground based lidars and a spectrometer. Althought the campaign was succesful, the low temperatures in the stratosphere caused several balloon failures, which after a thorough investigation were traced to the balloon film brittlness, and led to another technical campaign in January 1989 (see TECHNOPS campaign for details) that also was used to obtain scientific data.

On the basis of the succesful tests of that campaign, that showed that the problem was solved, a third effort named CHEOPS III was planned for the winter of 1989/1990 as a more ambitious field experiment. In addition to balloon-borne and ground based observations, the program included an increased number of regular ozone sonde launches at various Scandinavian stations, Spitzbergen Islands and Greenland. The goal was to investigate the composition of the winter lower Arctic stratosphere until early Febraury when the temperatures were at their lowest and the occurence of chemistry perturbation episodes was more likely.

The campaign was carried out from January 10 to Febraury 9, 1990 and a total of 10 balloon flights were performed, transporting instruments for Universities and Laboratories from France, Germany, Japan, United States and New Zealand.

The CHEOPS balloon flights have allowed to obtain the first measurements of Polar Stratospheric Clouds particles, water vapour, age-of-air using a cryosampler, NOx/NOy and HNO3 in the stratospheric vortex. Also, the first indications of the existence of
an Arctic ozone hole, though of less amplitude than in the Arctic, was derived from
a series of ozonesonde carried by the University of Wyoming in Kiruna.

This earlier effort would led in later years to more extensive campaigns like EASOE , SESAME and SOLVE-THESEO also focused on determining the amount and mechanism of the Ozone depletion in the Arctic.

Launch base	Date	Flight Duration	Experiment	Payload landing place or cause of the failure
ESRANGE	2/5/1987	---	ACIMS (Active Chemical Ionization Mass Spectrometer) + CRYOGENIC SAMPLER	--- No Data ---
ESRANGE	2/11/1987	---	CHEOPS	--- No Data ---
ESRANGE	2/1/1988	---	ACIMS (Active Chemical Ionization Mass Spectrometry) + CRYOGENIC SAMPLER	--- No Data ---
ESRANGE	2/10/1988	---	CRYOGENIC SAMPLER	--- No Data ---
ESRANGE	1/9/1990	---	LMD	--- No Data ---
ESRANGE	1/10/1990	---	ELHYSA (Etude de L'Hygromérie Stratosphérique) + Telemetry test	--- No Data ---
ESRANGE	1/11/1990	---	BONBON + CRYOGENIC SAMPLER	--- No Data ---
ESRANGE	1/13/1990	---	KR 007	--- No Data ---
ESRANGE	1/16/1990	---	KR 010	--- No Data ---
ESRANGE	1/18/1990	---	LOAL-LILLE	--- No Data ---
ESRANGE	1/18/1990	---	CNRS-SA	--- No Data ---
ESRANGE	1/19/1990	---	KR 013	--- No Data ---
ESRANGE	1/19/1990	---	ELHYSA (Etude de L'Hygromérie Stratosphérique)	--- No Data ---
ESRANGE	1/24/1990	---	KR 017	--- No Data ---
ESRANGE	1/26/1990	---	ELHYSA (Etude de L'Hygromérie Stratosphérique)	--- No Data ---
ESRANGE	1/27/1990	---	KR 023	--- No Data ---
ESRANGE	1/29/1990	---	KFA	--- No Data ---
ESRANGE	1/30/1990	---	KR 023	--- No Data ---
ESRANGE	1/30/1990	---	MPIK	--- No Data ---
ESRANGE	1/31/1990	---	CNRS	--- No Data ---
ESRANGE	1/31/1990	---	KR 025	--- No Data ---
ESRANGE	2/2/1990	---	KR 027	--- No Data ---
ESRANGE	2/5/1990	---	MPIK	--- No Data ---
ESRANGE	2/6/1990	---	PAYLOAD UNKNOWN	--- No Data ---
ESRANGE	2/8/1990	---	TECHNO BA	--- No Data ---
ESRANGE	2/9/1990	---	JUMBO + CRYOGENIC SAMPLER	--- No Data ---