Between the two SOLVE-II balloon flights, the JPL MkIV interferometer made 24 days of ground-based observations after the Sun returned to Esrange in late January.
These measurements allow us to observe the chemical evolution of the vortex from the winter to the spring. Of particular interest are the chlorine- and nitrogen-containing gases (e.g. ClO, HCl, ClNO3, NO, NO2, HNO3) that control the rate of ozone destruction.
Observations were performed by remote control from California.
The MkIV instrument viewed the Sun through a 6" diameter ZnSe window
which allows about two hours of solar observations each day.