Robust or not ?

[soklar]

I read the two articles entitled "Detecting trend ans seasonal changes in satellite image time series" and "Phenological change detection while accounting for abrupt and gradual trends in satellite image time series" and I would like to use the algorithm thanks to the bfast() function.
If I am not mistaken, these articles state that estimations of the different regression parameters are made in a robustly way (based on M-estimation). However, when I check the code of the bfast() function I cannot find these robust estimations. Indeed the lm() function is used rather than the rlm() function which I expected to.
Thus, my question is: Where in the code does the robust character appear ?

Thank you in advance for any answer.