A senior U.S. Senate Democrat this week ended an inquiry into operations of the University of Maryland University College, a fast-growing provider of public online education that came under scrutiny after the abrupt resignation of its president this year.

A top aide to Sen. Tom Harkin (D-Iowa), chairman of the Committee on Health, Education, Labor and Pensions, sent UMUC a letter indicating that questions about the university’s enrollment and workplace practices had been answered. Harkin in March had requested UMUC records after the unexplained departure of UMUC President Susan Aldridge.

“UMUC has a clear set of goals and priorities going forward, that if fully implemented will help to ensure its programs and practices meet the educational and career needs of the working adults, military personnel and other non-traditional learners that UMUC serves,” Pamela Smith, the committee’s staff director, wrote in the letter.

Javier Miyares, who succeeded Aldridge, hailed the letter as “a very important milestone” for a school that has more than 42,000 students this fall and educates more than 90,000 a year.

Aldridge, president of UMUC from 2006 until March, had faced internal criticism over her management style and academic priorities.

Miyares, who served under Aldridge, said he has sought in recent months to set a tone of tolerance and openness. In a May 21 letter to Harkin, Miyares and University System of Maryland Chancellor William E. Kirwan wrote that there had been a change in “existing culture [at UMUC] from one that includes a perception that dissension is punished toward one that treats employees fairly.”

Data UMUC provided to Harkin shed fresh light on how a public online university operates.

The university spent about $30 million — or about 8 percent of its revenue — on marketing and advertising in 2011. From 2006 to 2011, UMUC experimented with paying fees to contractors for finding prospective students via the Internet, a practice called “lead generation.”

UMUC told Harkin that in 2009, it paid a firm called Innovation Ads more than $10 million for lead generation. But the effort was discontinued after it fell short of goals. The university still advertises on the Internet, but it stopped purchasing leads from Internet aggregators.

Miyares said the university will continue to seek aggressive growth because that is the only way it can maintain academic standards and affordability. Annual in-state tuition and fees for full-time UMUC undergraduates is $6,474, according to the College Board.

The university is about to begin a new refund policy that could have a significant initial cost, Miyares said. Starting in 2013, students who enroll in a course will be allowed to try it for four days, he said. During that grace period, students will be able to obtain a full refund if they decide to quit the class. Miyares said the policy will promote “quality and student success.”