  XMM-Newton, a European Space Agency observatory, has been observing the
X-ray, ultra-violet and optical sky for 23 years. During this time, astronomy
has evolved from mainly studying single sources to populations and from a
single wavelength, to multi-wavelength or messenger data. We are also moving
into an era of time domain astronomy. New software and methods are required to
accompany evolving astronomy and prepare for the next generation X-ray
observatory, Athena. Here we present XMM2ATHENA, a programme funded by the
European Union's Horizon 2020 research and innovation programme. XMM2ATHENA
builds on foundations laid by the XMM-Newton Survey Science Centre (XMM-SSC),
including key members of this consortium and the Athena Science ground segment,
along with members of the X-ray community. The project is developing and
testing new methods and software to allow the community to follow the X-ray
transient sky in quasi-real time, identify multi-wavelength or messenger
counterparts of XMM-Newton sources and determine their nature using machine
learning. We detail here the first milestone delivery of the project, a new
online, sensitivity estimator. We also outline other products, including the
forthcoming innovative stacking procedure and detection algorithms to detect
the faintest sources. These tools will then be adapted for Athena and the newly
detected or identified sources will enhance preparation for observing the
Athena X-ray sky.
