Cosmos 1809 (Ionosonde ) satellite was launched on December 18, 1986 and had been operating till May 23, 1993, i.e. in the course of substantial portion of the 22-th cycle of solar activity. It was a three-axes stabilized spacecraft and was placed into a 960 km circular orbit at inclination of 82.5 deg. The satellite had the following scientific equipment on board 1. Ionosonde; 2. Impedance probe; 3. High-frequency probe; 4. Mass-spectrometer; 5. Photoelectron Spectrometer; 6. Electric Fields Detector; 7. Low-Frequency Waves Analyser; 8. High-Frequency Waves Analyser. The ionosonde, the mass-spectrometer and the photoelectron spectrometer ceased operations in 1987; the remaining instruments listed above were active till the satellite demise. The satellite equipment worked in four memory regimes 1, 2, 3 and 4 with sampling frequencies of 100 Hz, 12 Hz, 3 Hz, and 0.04 Hz, correspondingly. More details concerning the satellite instrument package are presented in file equipm.txt. The data of the experiments on board of Cosmos-1809 satellite can be used for the fundamental researches of the following near Earth physics issues: - the ionosphere-magnetosphere coupling in different geophysical conditions; - global structure of the ionosphere and its modification caused by solar and geomagnetic activity; - strong earthquakes influence on the ionosphere and seismic precursors in the ionosphere; - nonlinear processes in the ionosphere plasma under impact of the intensive radio waves; - propagation of VLF and HF-emissions in the ionosphere and the magnetosphere; - diagnostic of the man-made impacts on the ionosphere. Raw satellite data are stored on magnetic tapes in the form of telemetry data. There is about 500 periods of measurements in the course of more than 6 years of the satellite operation (see file catall.txt), the total data volume is about 7.5 Gbytes. The quality of tapes is far from perfect and data will be lost in near future. In the framework of data rescue project it is planned to process data for about 50 intervals during different anomaly events (earthquakes, active experiments including release of substance in the ionosphere, heating of the ionosphere by HF waves at the Soura facility in Russia and so on). The list of selected orbits is presented in cat1.txt file. It is open for amendments. For these orbits the following physical parameters along the satellite path will be obtained: 1. Electron density and its irregularities; 2. Electron temperature; 3. DC electric field; 4. AC electromagnetic field of various frequencies. Approximate size of data set will be about 500 Mbytes and it is planned to produce a CD. The software package attached to the CD will allow data selection and browse in MS-DOS operation system. Data output in the form of graphics will be included. Samples of the satellite processed data are presented in files fig1.exe - fig4.exe. Those interested in more details concerning Cosmos 1809 data should address Dr. Yu. Romanovsky: Institute of Applied Geophysics, Rostokonskaya str. 9, 129226 Moscow, Russia fax: 7-095- 187-7513 or 181-0591 E-mail: geophys@sovamsu.sovusa.com or cengeo@glas.apc.org Literature 1. Y. Romanovsky, D. Pulinets. The Availability of Data in the Former Soviet Union-Part3. Ionosonde. STEP International, 1993, v3, N3, p.4. 2. V. M. Kostin, Yu. A. Romanovsky, V. M. Chmyrev et al. Satellite Investigations of the Disturbances of the Outer Ionosphere Due to Modification of the Ionospheric F-region by High-Power HF Radio Waves. Cosmic Research, 1993, v31, N1, p.67 (A translation of Kosmischeskie issledovania). 3. S. I. Avdjushin, S. I. Kozlov, Yu. A. Romanovsky et al. "Active experiments and Antropogenic Effects in the Ionosphere." Cosmic Research, 1993, v31, N3, p.1. 4. S. A. Pulinets, Prospects of Topside Sounding, WITS handbook N2, Chapter 3, SCOSTEP Publishing, Urbana, Illions, p.99-127. 5. S. A. Pulinets, Russian satellite data base for use in ionospheric mapping, Procceedings of PRIME/URSI joint Workshop: Data validation of ionospheric models and maps, Roquetes, 1992, Publ. Abs. del Ebro, Mem. N16, p.105-110. 6. A. T. Karpachev and S. A. Pulinets, IRI model with topside sounding data in the light of Global longitudinal effect, Proceeding of PRIME/URSI joint Workshop: Data validation of ionospheric models and maps, Roquetes, 1992, Publ. Obs. del Ebro Mem. N16, p. 93-99.