The plot below is an approximation of the number of coordinated instrument hours per day over the course of the entire SOHO mission (until 2002/11/03). It is based on all the KAP (Keyword Activity Plan) files which is again based on IAPs (Instrument Activity Plan).
The KAP activities have been cross-referenced with the campaign database in such a way that whenever one instrument flags a campaign activity, all instruments (except CDS, SUMER, UVCS and TRACE) participating in that campaign (according to the campaign database) are flagged as participating. So, for i.e. campaigns with EIT synoptics & CME Watch as part of the support, EIT will be counted. CDS, SUMER, UVCS and TRACE are being kept out since they should in principle have campaign numbers for all campaign observations.
The data below has been smoothed with a 20-day full-width-to-half-maximum (FWHM) Gaussian to eliminate severe short-time noise, and plotted in an incrementally summed fasion (i.e., the SUMER line is really SUMER + CDS, the UVCS line is UVCS+SUMER+CDS etc). The (perhaps surprising) large peaks during 2002 are in part related to the Max Millennium campaigns (Default RHESSI support and Major Flare Watches).
Below is the same dataset, smoothed with a 180-day FWHM Gaussian.