SICH-1 - Ukraine's Oceanographic Satellite

Note: This satellite is no longer active

Overview

One of the most fascinating features of the 137 MHz weather satellite band were the transmissions from SICH-1, Ukraine's first oceanographic weather satellite. Unlike the NOAA orbiters familiar the world over, SICH offered RADAR and thermal microwave imagery in addition to the more usual visible light transmissions.

SICH-1, which was launched early in September 1995, was identical with the Okean series of satellites that had been operated by Russia; not altogether surprisingly, since Ukraine in fact manufactured the Okeans for the former USSR.

Approximately three quarters of transmissions from SICH were recorded over distant areas of the Earth, and consequently images could frequently show exotic and unfamiliar locations.


Instrumentation

Instrumentation carried by SICH consisted of MSUM, a 4-channel scanning radiometer, SLR, the X-band sideways looking synthetic aperture RADAR, and RM, the microwave radiometer. Transmitted images could be from various combinations of these instruments, as illustrated. The scanning radiometer had four channels, 0.5-0.6 nm; 0.6-0.7 nm; 0.7-0.8 nm and 0.8-1.0 nm. The last of these, approximating to the channel-2 imagery from the NOAA satellites, was almost always the one transmitting. From SICH's altitude of 650 km (400 miles) the swath width of the radiometer images was 1900 km (1200 miles), and provided, at the sub-satellite point, cross-track resolution down to 1 km and along-track resolution of 1.7 km.

The RADAR scanner had a carrier frequency of 9.52 Ghz (a wavelength of 3.15 centimetres). Its swath width was 450 km (280 miles) with an incidence angle of 20 at the swath's near edge. Spatial resolution was 1.3 km cross-track and 2.5 km along-track. The microwave radiometer operated in the 36.5 - 36.8 Ghz frequency band (wavelength 8 millimetres) and a swath width of 550 km ( 340 miles ). Sensitivity was 3.7 kelvin, and the spatial resolution was 25 km in both directions.

Additionally, the satellite carried instrumentation transmitting higher resolution imagery at a frequency of 465 MHz. As far as it is understood, no amateur ground station capable of decoding these transmissions ever existed. Because of the high energy requirements of the instrumentation, SICH only transmitted radar in short bursts. The RADAR could only operate for 15 minutes at a stretch and a pause of at least 30 minutes was required before it could be re-activated. The scanning radiometer, MSUM, could operate uninterrupted for a maximum of 30 minutes, though in practice seldom more than eight. A break of at least 70 minutes was required before the radiometer could be activated once more.


Imagery

Approximately one quarter of SICH's transmissions were 'live', real-time images centred on the region between the Baltic Sea and the Eastern Mediterranean. Nearly all of these were RADAR-only transmissions. The remainder of SICH's output consisted of images recorded over distant parts of the Earth, such as Alaska, Australia, Antarctica, South America, the Persian Gulf and the Far East. These were transmitted when SICH came within range of one of its ground stations. Although the schedules indicated which transmissions were to be of recordings, there was no clue as to which part of the Earth was to be imaged, so there was always a sense of wonder as the image decoded.

Often, it was not immediately apparent where the image was recorded, specially if conspicuous land features were absent. But SICH had a secret up its sleeve. With the exception of the RADAR-only images, SICH images were always accompanied by an edge-code of numbers and greyscales. The single four-digit number sandwiched between the white block and the greyscale wedge was the satellite's onboard clock time. It is Moscow time, expressed in minutes after midnight. Since Moscow time is 3 hours ahead of GMT, it took just a little effort with a satellite tracking program to determine the location of SICH when the recordings were made.