## 5 Conclusions  
A generic framework for an End-to-end Instrument Performance Simulation System (EIPS) for the satellite atmospheric remote sensing instruments has been developed and presented in this paper. The EIPS framework was derived from a systematic atmospheric observing system design (AOSD) process, as described in Rodgers (1988). This useful AOSD process was first visualised (as a schematic block diagram) in the paper and then taken as a reference guideline to build the framework. The EIPS has been built around the HT-FRTC (an atmospheric radiative transfer model) to form a complete simulation framework that can be used for instrument performance analysis and simulation tasks (such as trade-off analysis and design parameter optimisation). The design and the organisation of EIPS components (sensor parameter model, HT-FRTC model and the information and error analysis model) have been described. The EIPS framework offers fast radiative transfer simulation capability, any number of satellite remote sensing instruments can be simulated, and it is flexible to new and emerging technology-based sensors. To demonstrate the flexibility of the framework, a novel superconducting TES-based multi-spectral MW instrument has been presented as an example. In the last section of this paper, we further applied the EIPS framework by conducting a case study (as an example of framework's application), in which we analysed the relative performance of three MW instrument configurations (A, B and C). The results on the relative performance of these three MW instrument configurations (two configurations (A and B) are based on existing multi-spectral MW instruments and the third configuration (C) is based on emerging technology) have been presented. Configuration A and B were based on the existing ATMS and AMSU-A instruments respectively. Configuration C in this paper is based around recently emerging superconducting TES-based filterbank spectrometer technology. For the purposes of this paper, we modelled a relatively simple instrument with the same channel configuration as ATMS-type instrument (Configuration A), but with the greatly improved noise performance offered by this technology. EIPS experimental simulations have shown that when comparing configuration A and B, configuration B (an AMSU-A-type instrument) provided a relatively high information content on temperature as compared to configuration A (an ATMS-type instrument). This improvement can be mainly attributed to the low instrument noise in the temperature sounding channels of AMSU-A-type instrument. But, in the case of humidity, configuration A (ATMS-type) provided relatively more information compared to configuration B; this improvement is mainly because configuration A contains five extra humidity sounding channels around 183.31 GHz water vapour absorption line. While comparing all three configurations, we observed that configuration C (a TES-based MW instrument) provides the highest information content on temperature and humidity. As configuration C has exactly the same channel configuration as configuration A, this improvement in information content can be directly attributed to the much lower radiometric noise in each channels of configuration C. This demonstrates that the radiometric noise (NEDT) is an important factor in improving the retrieval error performance of the instrument. The technology (on which the configuration C is based) offers greatly improved noise performance, and it allows the implementation of potentially thousands of sounding channels ranging from \(\sim\)30 GHz up to \(\sim\)850 GHz with very narrow spectral bandwidths. This opens up some very exciting new instrument concepts and sounding capabilities. The developed EIPS framework in this paper will be used for performance simulations and trade-off studies to find an optimal configuration for a _hyperspectral MW_ instrument based on this emerging superconducting TES-based filterbank spectrometer technology, which will be the subject of our next paper.