Support levels for spx:
1530 and rising a point each day - 50dma
1521 - trend line from lows in nov and early january, very important support, if broken,then the rally is for sure over, but another rally up to touch it again is likely.
1515 and rising slowly - lower bollinger band
Today is not a bottom, still more downside next week, but I bet above supports will hold, which one is the question.