The GMRT-EoR Experiment: A new upper limit on the neutral hydrogen power
  spectrum at z~8.6
  We present a new upper limit to the 21cm power spectrum during the Epoch of
Reionization (EoR) which constrains reionization models with an unheated IGM.
The GMRT-EoR experiment is an ongoing effort to make a statistical detection of
the power spectrum of 21cm neutral hydrogen emission at redshift z~9. Data from
this redshift constrain models of the EoR, the end of the Dark Ages arising
from the formation of the first bright UV sources, probably stars or
mini-quasars. We present results from approximately 50 hours of observations at
the Giant Metrewave Radio Telescope in India from December 2007. We describe
radio frequency interference (RFI) localisation schemes which allow bright
sources on the ground to be identified and physically removed in addition to
automated flagging. Singular-value decomposition is used to remove remaining
broadband RFI by identifying ground sources with large eigenvalues. Foregrounds
are modelled using a piecewise linear filter and the power spectrum is measured
using cross-correlations of foreground subtracted images.
