LOFAR, the LOw Frequency ARray radio telescope, is designed, among other things, to measure the neutral hydrogen fraction in the Universe as a function of redshift, through the hydrogen hyperfine 21cm line. The LOFAR Epoch of Reionization (EoR) key science project is the project that will carry out this very challenging observation and analyze its results. The project will map the Universe's Epoch of Reionization in a number of fields of view with arc-minute resolution. Each field will contain about a 100 square degree over 115-190MHz frequency range (i.e., redshifts range of about 11.5-6.5).
The EoR measurement is very challenging for a number of reasons:
- The signal will be contaminated by very prominent galactic and extragalactic foregrounds.
- The sky signal goes through an ever changing ionosphere that can severely distort the signal.
- Given the nature of the LOFAR instrument, modeling the telescope with time will be very challenging.
- The thermal noise per resolution element, even after hundreds of hours of observation will dominate over the signal.
All these issues have to overcome before a reliable detection of the EoR could be claimed.