[1] Both uncrewed orbiters were to map the surface of Venus using high resolution imaging systems.
No transmissions were possible, so the orbit of Venera 16 was rotated back 20° at this time to map the areas missed during this period.
Each spacecraft consisted of a 5 m long cylinder with a 0.6 m diameter, 1.4 m tall parabolic dish antenna for the synthetic aperture radar (SAR) at one end.
During imaging, the radio altimeter would be lined up with the center of the planet (local vertical) and the SAR would be looking off to the side at 10 degrees.
A bulge at the opposite end of the cylinder held fuel tanks and propulsion units.