First Results of the SCIAMACHY Mission

The following results are based on the analysis of uncalibrated data, taken from ESA for the commissioning phase of SCIAMACHY. The results are thus taken to be preliminary. Up to now one can say that SCIAMACHY is in good shape. After SODAP, first calibration activities, a first validation week (18.7. - 25.7.) and a week of thermal activities (esp. non-nominal decontamiantion) SCIAMACHY is now ready for validation since the beginning of August.

Starting at the beginning of August, SCIAMACHY performs nominal measurements (alternating limb-nadir, solar and lunar occultations/calibration, daily, weekly and monthly calibration) until the end of November.

Details of the planned measurement sequences and the predictions for limb/nadir overpasses can be found at the SOST home page. The predictions for the August and September overpasses are currently posted there. Overpass information can also be found at the validation pages.

During an instrument review at the end of July it was reported that all measurement modes are tested and working as expected. The thermal performance of the instrument is well characterised and the instrument operates under nearly stable thermal conditions. Optical performance is as expected, with the exception of channels 7 and 8 (see below). For example, radiometric calibration of the solar irradiance is within a few percent of the on ground calibration and spectral stability over the orbit is very high (1/100 pixel).

One major anomaly was reported during June, namely the contamination of channels 7 and 8 by ice. Ice on channels 7 and 8 leads to a temporary loss in transmission of more than 50% in those channels. Nominal and non-nominal decontaminations were performed and had demonstrated that the ice layer can be removed by heating (parts of) the instrument. Work is in progress to develop a procedure to minimise the impact of the contamination on the data quality. Despite this contamination, the retrieval of CO from channel 8 data was demonstrated to be feasible.

The first successful "ballooning of SCIAMACHY" was the flight of the "IASI balloon" (PI: C. Camy-Peyret) on 5 August 2002 resulting in coincidences with two nadir and one limb SCIAMACHY measurments. Additional balloon launches took place in Kiruna on August 8, 12 and 18 (see campaign information ). The Canadian Mantra balloon will be launched soon.

In the comming weeks SCIAMACHY will continue to perform the nominal measurements during the validation campaigns. Some remaining calibration and engineering activities are scheduled in such a way that they will not interfere with the campaigns. Note that between September 8th and 11th, ESA will perform an Orbit Control Manoeuvre (OCM) and the upgrade of the ENVISAT PMC s/w is planned. This requires that all instruments will be switched off.

Processor verification activities are ongoing and first results will be reported at the ENVISAT Calibration Review (ESTEC, 9-13.9.2002). First results on validation of SCIAMACHY products will be reported at the Validation Review in the second week of December.