IEEE Geoscience and Remote Sensing Magazine - September 2023 - 11

signal processing. A prototype airborne system allowing
in-flight testing was also designed, and systematic flights
onboard a dedicated MI-8 helicopter were organized. Besides,
it was decided to add another passive sensor to the
SLR, working in the millimeter-wave range-a Ka-band radiometer,
also developed at IRE. Moreover, to produce the
images, an onboard electronic data processing block was
developed at DBP and IMH and added both to the airborne
prototype and to the orbital system.
The very first airborne experiments soon confirmed the
high efficiency of the designed instruments for studying the
water and ice surfaces [17], [18], [19], [20]. The joint use of
microwave images obtained from the X-band SLR and Kaband
radiometer offered, in principle, more efficient study
of the state of the sea and ice than using the data from each
individual sensor. However, initial tests had also shown
that obtaining reliable information on the water-surface
waving needed a much deeper level of data processing than
available at that time. In contrast, quite reliable data were
obtained in a simpler way in the helicopter observations
of ice. The results of airborne studies convinced Kalmykov
of the favorable prospects for radar observations of sea ice
from space.
Still, attempts to interpret the ice-sounding data beyond
simple discrimination between thin and thick ice
did not lead, unfortunately, to the creation of an adequate
model. The phenomenon of the scattering from the ice
turned out to be much more complicated than the scattering
from the water surface. Still, other possible applications
emerged, such as wind measurements and oil slicks
detection [18], [20].
The Cosmos-1500 satellite (Figure 2) was launched on
28 September 1983 from Plesetsk by the Tsyklon-3 rocket
vehicle (a derivative of a heavy ICBM SS-18) and placed
into low-altitude near-circular polar orbit. It remained
operational until 16 July 1986. This was the first ever civil
satellite to carry an X-band RA-SLR working at the wavelength
of 3.16 cm with vertical polarization; the swath
width was about 460 km, and the spatial resolution was
2.4-3.2 km in the flight direction and 1.3-0.6 km in the
normal direction [4], [22], depending on the incidence
angle (see Table 1).
The antenna system was based on the 12-m-long slotted
waveguide, which was kept folded at the launch and
then automatically unfolded in orbit. This radar was supplemented
with a 37-GHz horizontally polarized sidelooking
passive radiometer, designed at IRE NASU, and
a four-channel visible range imaging system from the Institute
of Radio-Engineering and Electronics (IRE RAS) in
Moscow. The polar orbit was selected to provide data on the
ice conditions in the Arctic in the hope to be useful for the
navigation of ships in the northern latitudes, which were
not visible from geostationary satellites. The chosen RASLR
parameters were considered as optimal for all-weather
studies of the polar sea ice covers and the dynamics of ice
formation, migration, and melting.
SEPTEMBER 2023 IEEE GEOSCIENCE AND REMOTE SENSING MAGAZINE
Besides carefully selected radar parameters, the high
efficiency of the SLR Cosmos-1500 system was expected
due to the simultaneous acquisition of overlapping images
from two other sensors so that three different wavelength
bands were involved. This could enable the improved interpretation
of images and the elimination of errors in
retrieved parameters. Further, the onboard preliminary
processing of the radar data and the transmission of the
8
7
2
4
3
2
3
3
5
3
6
FIGURE 2. Cosmos-1500 and its microwave remote sensing instruments:
(1) bus, (2) solar panels, (3) rotatable instrument panels,
(4) SLR antenna, (5) radiometer, (6) optical sensors, (7) telescopic
mast, and (8) gravitational stabilizer [3].
TABLE 1. PARAMETERS OF THE SLR OF COSMOS-1500.
Wavelength
Polarization
Viewing angle range
Antenna pattern width
In the azimuthal plane
In the elevation plane
Spatial resolution
Along the flight direction
Transverse to the flight direction
Average resolution in the swath, provided via APT
In the UHF band
In the VHF band
Receiver sensitivity
Transmitter power
Pulse duration
Pulse repetition frequency
Orbit altitude
Orbital inclination
Swath
3.1 cm
VV
20-46°
0.2°
42°
2.4-3.2 km
1.3-0.6 km
0.8 × 2.5 km
2 × 2.5 km
−140 dB/W
100 kW
3 µs
100 Hz
650 km
82.6°
450 km
Reproduced from [4] after correction of typos and translation mistakes.
VV: vertical transmit-vertical receive.
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IEEE Geoscience and Remote Sensing Magazine - September 2023

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