Raducanu and Richardson initially linked up in April for a four-day training stint at the Ferrer Tennis Academy in Spain, where Richardson has been the tennis director for several years.
She announced they were reuniting on a full-time basis earlier in May and has now confirmed they will work together for the rest of the season.
“We kept on good terms and it was one of those moments when the timing was right,” Raducanu, who initiated the move by sending Richardson a text, told BBC Sport.
“He doesn’t care about the noise and is really good at centring me.”
Raducanu’s first match back under Richardson’s guidance ended in a straight-set defeat by France’s Diane Parry in Strasbourg last week.
She arrived at Roland Garros having barely played in the past three months because of the lingering effects of a viral illness, but Raducanu resisted the temptation to skip the clay-court major.
“There was definitely the option to start on the grass straight away,” she said.
“Putting the miles in the legs on the dirt will help me for next year’s clay-court season, help build up the physical and technical skills, and getting competitive match practice so I’m not starting at ground zero.
“I’m pleased I made this decision to play and regardless of results I know it is the right one.”