NASA's Wide-Field Infrared Survey Telescope (WFIRST) is expected to become a formal project next month, about a year earlier than initially planned. The decision was made after the US Congress provided $90m for WFIRST for the 2016 fiscal year – significantly more than the $14m NASA had requested.

With an estimated cost of $1.6bn, WFIRST is expected to launch in the next decade, and was listed as the top priority for NASA in its 2010 decadal survey carried out by the National Research Council. The probe is seen as a successor to the planned James Webb Space Telescope, which is set to launch in 2018.

One key scientific objective of WFIRST is to make "definitive measurements" of dark energy and the growth of structures in the universe. It will also aim to directly image exoplanets and take spectroscopic measurements of their atmospheres. "This is all part of NASA's overarching high-priority science goals to understand the nature of the universe that we live in and whether we are alone in it," says WFIRST programme scientist Dominic Benford.

Refurbished spy satellite

WFIRST will use a telescope given to NASA by the National Reconnaissance Office – a US government agency that builds and operates spy satellites. Although the telescope was designed for surveillance of targets on Earth, its capabilities are compatible with the goals of WFIRST. The telescope's 2.4 m primary mirror is the same size as the Hubble Space Telescope, but its field of view is 100 times larger, allowing it to capture more of the sky with less observing time. Over the course of the six-year primary mission, WFIRST will measure light from a billion galaxies and perform a gravitational micro-lensing survey of around 2600 exoplanets.

According to Benford, WFIRST is currently defined as "an option that NASA could choose to pursue". Yet he says that with the funding boost, it is now expected to become an official project in February. WFIRST will also be made available to the scientific community, through a competitive process, for a quarter of its mission time.