Having such a precise yardstick allowed Russian dynamicists Gregoriy A. Krasinsky and Victor A. Brumberg to calculate, in 2004, that the sun and Earth are gradually moving apart. It’s not much – just 15 cm per year – but since that’s 100 times greater than the measurement error, something must really be pushing Earth outward.
That's New Scientist, after all. Here's a better reference: Values of some astronomical parameters - AU, GM, M of the Sun, their possible variations from modern observations, and interrelations between them.
The author of that paper, Elena V. Pitjeva, worked closely with Krasinsky and Brumberg. She was one of Krasinsky's students and continued working with him at the prestigious Russian Academy of Sciences's Institute of Applied Astronomy (essentially the Russian equivalent of JPL with regard to ephemerides).
In that conference paper she describes what that paper by Krasinsky and Brumberg found. First off, they were writing about possible secular variations in the Astronomical Unit (au). That is not quite the mean (average) distance between the Sun and the Earth. It's close, but the semi-standard and widely used definition used at the time of the paper by Krasinsky and Brumberg was convoluted (and that's putting it nicely).
The key problems with the paper by Krasinsky and Brumberg were that
- The definition of the au they were using was rather convoluted.
- They used a 42 year span of time. the space era marks the onset of reliable, high quality data needed for ephemerides.
- They tried to simultaneously estimate the value of the au and its rate of change (along with a whole lot of other parameters in their ephemeris generation).
- The derived values of the au and its rate of change were very highly correlated; 98.5% per Pitjeva's paper.
Pitjeva's takeaway was that we simply don't have enough data (yet) to reliably estimate the rate at which the Earth is receding from the Sun. It should be receding to some extent as the Sun has to be losing mass. (I wrote "has to be" in scare quotes because while it is losing mass due to fusion and solar wind, it is also gaining mass due to infalling material. No sane solar scientist thinks the mass gain is anywhere close to the mass loss.)
However, an unmodeled 15 cm/year Earth recession rate would be more than enough to observationally interfere with JPL's ability to communicate with NASA's deep space probes. JPL does not currently model this. It doesn't even model the estimated mass loss rate of the Sun. It's below the observational threshold. 15 cm/year is not below the observational threshold.