From last solar conjuction (2004)
"Based on experience with other spacecraft, we expect that when the Mars-Sun-Earth angle is 2 degrees or less, the ability to successfully communicate degrades rapidly," said JPL systems engineer Scott Doudrick, who has been organizing conjunction operations for both rovers. "To be cautious, we're allowing three days on either side of that period."
The planned gap in sending daily plans runs for about 12 days beginning Sept. 8 for Spirit and Sept. 9 for Opportunity. The rovers will be instructed ahead of time to continue doing atmospheric operations and Mössbauer spectrometer readings daily during that period. No movements of the wheels or the robotic arms are in the conjunction-period plans, but the camera masts may move for making observations. The rovers also will continue communicating daily with NASA's Mars Odyssey orbiter and will also attempt to communicate directly with Earth.
Looks like Spirit could be out of touch on S1K.