This answer shows the first image below of a vintage view of the ISS. Only one of each triplet of thermal radiators is extended from each TRRJ.
The ISS' solar panels articulate to modulate the incidence of sunlight in order to present maximum cross-section when power is needed most and possibly less cross-section when power generation isn't needed and power is dumped into ballast resistors, as well as to sometimes decrease aerodynamic drag and need to reboost when the station is in eclipse.
- When there is more power than needed, are satellite photovoltaics shunted or open circuit?
- How are the orientations of the ISS' eight independent solar arrays optimized?
But my thinking is that
- radiators are designed to be fairly solar-blind so presumably one wouldn't gain a lot by tilting them away from the Sun,
- The position of the Earth (also a source of radiative loading) is always the same relative to the ISS' orientation, or at least it better be!
- "the cold of space" in which to radiate is always the upper half hemisphere (see 2.)
So why do the ISS' TRRJs need to tilt?
From Wikipedia's External Active Thermal Control System :
Heat Rejection - Ammonia passes from the ATA through a two way path of the Flex Hose Rotary Coupler (FHRC) where heat captured while passing through the Heat Exchangers is directed to be expelled through the Heat Rejection System Radiators (HRSRs). The radiators are rotated by the Thermal Rotary Radiator Joint (TRRJ) which continually rotates the radiator wing for optimum cooling.
Source open for full size view!