Echelle Spectroscopy of the Stardust SRC Entry

Peter Jenniskens, Carl Sagan Center, SETI Institute
We describe the reduction of optical spectra from the Stardust Sample Return Capsule's atmospheric entry on January 15, 2006, obtained by means of a slit-less miniature Echelle spectrograph onboard NASA's DC-8 Airborne Laboratory. The data cover the wavelength range 370 to 880 nm, at 0.14 - 0.9 nm resolution, during the time interval when radiative heating was most important. The data contain a broadband continuum, presumably from the hot heat shield surface, shock layer air plasma emissions of N, O, and N2+, atomic hydrogen and CN molecular band emission from the ablating heat shield material PICA, as well as, early in flight, atomic lines of Zn, K, Ca+, Ca, and Na from a Z-93P paint applied to the top of the PICA. At each moment along the trajectory, the whole spectrum is recorded simultaneously but broken into smaller segments. Key issues addressed in the data calibration concerned: 1) the varying position of the Echelle pattern on the CCD as a function of the position of the SRC in the field of view, 2) the proximity of the Echelle orders, and 3) the camera response.