Next steps for LISA
The space-borne gravitational wave detector LISA has been studied in great detail over the last decade as a collaborative mission between ESA and NASA.
As announced by ESA in March 2011, due to a modified international cooperation scenario, it is now necessary to study a European-only mission that offers a significant reduction of the cost while maintaining its core science objectives. In the context of the reformulation exercise LISA has become the New Gravitational wave Observatory (NGO).
Whilst maximizing the use of results of the LISA studies performed so far and the heritage from LISA Pathfinder, a number of significant changes to the payload, the spacecraft and the mission architecture have to be made to enable the mission to fit the new budget profile.
Additionally, support from Member States in the payload area, where much experience has already been gained with the LISA Pathfinder mission, will be sought.
The workplan to achieve the above target includes:
- a preparatory phase to identify possible mission architecture and design options with the relative impact on science return;
- the validation and trade-off of design options in the ESA Concurrent Design Facility (CDF);
- the selection of one baseline to be studied in more detail until November 2011 with ESA technical experts and with industrial support.
The goal is to be ready for a technical and programmatic review starting in November 2011 and for a scientific review by the ESA advisory bodies thereafter, in order to support an SPC downselection for entering phase A/B1 in February 2012.
Preparatory phase
The goal of this phase is to identify a few mission profiles that can achieve a substantial cost reduction whilst minimizing the impact on the science return. Cost data from the recently completed Cosmic Vision L-mission downselection review will be used as a starting point.
Initially the elements that can lead to cost reductions will be identified. Subsequently new mission configurations that rely on changes in the areas identified will be analyzed.
In parallel, the parameter estimation software will be run to quantify the impact of the possible changes on the scientific return.
CDF study
The purpose of the CDF study is to enable the project team to make informed decisions, knowing the impact of design choices on the cost of the mission as well as on the expected scientific performance.
The project, together with the LISA Science Working Team, is looking at potential changes to the mission in the following areas, to be validated by the CDF activity:
- mission requirements: sensitivity; orbits; arm length; duration; operations;
- mission architecture: mothership/daughtership; 2 arm-configuration (four links);
- payload: complexity of optical layout; number of optical systems; single/double test mass; in-field guidance;
- spacecraft architecture: communication (laser link); electrical architecture;
- propulsion module: simplification (based on selected orbit);
- launch vehicle: identification of optimal LV (based on selected orbit); single/multiple launch scenario.
At the end of the CDF activity one mission scenario will be selected to be further studied in detail.
Feasibility study
Based on the CDF output, one mission design will be studied in detail for feasibility assessment and mission design.
This activity will be coordinated by the project and supported by ESA engineers and by industry in a technical consultancy role.
The selected mission architecture will maximize the use of elements developed in the frame of the LISA Pathfinder project or already studied in the LISA mission formulation activity.
It is expected that this study will produce a mission design and architecture compatible with the mission and the scientific requirements to be further refined in the subsequent phase A/B1 study.
The output of this activity will be a technical and a programmatic document that will be reviewed in the fourth quarter of 2011.