We observed comet 322P/SOHO 1 ( P/1999 R1 ) from the ground and with the Spitzer Space Telescope when it was between 2.2 and 1.2 AU from the Sun .
These are the first observations of any SOHO -discovered periodic comet by a non-solar observatory , and allow us to investigate its behavior under typical cometary circumstances .
322P appeared inactive in all images .
Its lightcurve suggests a rotation period of 2.8 { \pm } 0.3 hr and has an amplitude \gtrsim 0.3 mag , implying a density of at least 1000 kg m ^ { -3 } , considerably higher than that of any known comet .
It has average colors of g ^ { \prime } - r ^ { \prime } = 0.52 { \pm } 0.04 and r ^ { \prime } - i ^ { \prime } = 0.04 { \pm } 0.09 .
We converted these to Johnson colors and found that the V - R color is consistent with average cometary colors , but R - I is somewhat bluer ; these colors are most similar to V- and Q-type asteroids .
Modeling of the optical and IR photometry suggests it has a diameter of 150–320 m and a geometric albedo of 0.09–0.42 , with diameter and albedo inversely related .
Our upper limits to any undetected coma are still consistent with a sublimation lifetime shorter than the typical dynamical lifetimes for Jupiter Family Comets .
These results suggest that it may be of asteroidal origin and only active in the SOHO fields of view via processes different from the volatile-driven activity of traditional comets .
If so , it has the smallest perihelion distance of any known asteroid .