Relativistic collisonless shocks propagating in plasmas are an essential ingredient to explain particle accelerators such as gamma-ray bursts, supernovae remnants, pulsar and stellar winds. Numerical simulations predict particle energy distributions but these are very difficult to test because of the lack of simultaneous observation over 20 decades of frequency, complex geometries or variability. We propose to use SPIRE in the Small Map configuration to map the infrared emission of a very energetic and old pulsar wind nebula recently detected by HESS. Exploiting the unique resolution and sensitivity of SPIRE at 250, 350 and 500 mu m, we aim at detecting the faint synchrotron emission that will be compared to existing measurements in the radio, X-rays and gamma-rays. These wavebands, located between the CMB and dust emission, are centered where the synchrotron emission from the predicted relativistic Maxwellian distribution peaks, providing a constraining flux measurement.
Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.