Preparation for the Solar system observations with Herschel: Simulation of Jupiter observations with PACS

Abstract

Observations of the water inventory as well as other chemically important species on Jupiter will be performed in the frame of the guaranteed time key project of the Herschel Space Observatory entitled "Water and related chemistry in the Solar system". Among other onboard instruments, PACS (Photodetector Array Camera and Spectrometer) will provide new data of the spectral atlas in a wide region covering the far-infrared and submillimetre domains, with an improved spectral resolution and a higher sensitivity compared to previous observations carried out by Cassini/CIRS (Composite InfraRed Spectrometer) and by ISO (Infrared Space Observatory). In order to optimise the observational plan and to prepare for the data analysis, we have simulated the expected spectra of PACS Jupiter observations. Our simulation shows that PACS will promisingly detect several H2O emission lines. As PACS is capable of spatially resolving the Jovian disk, we will be able to discern the external oxygen sources in the giant planets by exploring the horizontal distribution of water. In addition to H2O lines, some absorption lines due to tropospheric CH4, HD, PH3 and NH3 lines will be observed with PACS. Furthermore, owing to the high sensitivity of the instrument, the current upper limit on the abundance of hydrogen halides such as HCl will be also improved.