We report photometric observations for comet C/2012 S1 ( ISON ) obtained during the time period immediately after discovery ( r =6.28 AU ) until it moved into solar conjunction in mid-2013 June using the UH2.2m , and Gemini North 8-m telescopes on Mauna Kea , the Lowell 1.8m in Flagstaff , the Calar Alto 1.2m telescope in Spain , the VYSOS-5 telescopes on Mauna Loa Hawaii and data from the CARA network .
Additional pre-discovery data from the Pan STARRS1 survey extends the light curve back to 2011 September 30 ( r =9.4 AU ) .
The images showed a similar tail morphology due to small micron sized particles throughout 2013 .
Observations at sub-mm wavelengths using the JCMT on 15 nights between 2013 March 9 ( r =4.52 AU ) and June 16 ( r =3.35 AU ) were used to search for CO and HCN rotation lines .
No gas was detected , with upper limits for CO ranging between 3.5-4.5 \times 10 ^ { 27 } molec s ^ { -1 } .
Combined with published water production rate estimates we have generated ice sublimation models consistent with the photometric light curve .
The inbound light curve is likely controlled by sublimation of CO _ { 2 } .
At these distances water is not a strong contributor to the outgassing .
We also infer that there was a long slow outburst of activity beginning in late 2011 peaking in mid-2013 January ( r \sim 5 AU ) at which point the activity decreased again through 2013 June .
We suggest that this outburst was driven by CO injecting large water ice grains into the coma .
Observations as the comet came out of solar conjunction seem to confirm our models .