Prospect Park's Closing Is Scaled Back Parts of Prospect Park in Brooklyn will remain open on Friday, despite a presidential visit, the Prospect Park Alliance said on Thursday, contradicting earlier information that it would be closed from noon to 6 p.m. President Obama, who has used heliports in Lower Manhattan when visiting New York, is to appear at a high school. Two Marine Corps helicopters were seen landing in the park on Tuesday in an apparent preparatory drill. In a statement on its Web site, the Prospect Park Alliance initially said that the park would be entirely closed on Friday "due to security associated with the president's visit." At least one event planned for that day, a wedding, was canceled. But on Thursday evening the alliance removed its statement, replacing it with one that said "only portions of Prospect Park will not be accessible," and apologizing for any inconvenience caused by the different messages. A spokesman for the alliance, Eric D. Landau, declined to comment on which areas of the park might be off-limits and on the reason for the change in plans.