An employee subject to this subtitle shall receive the following written performance appraisals at 6–month intervals based on the employee’s entry–on–duty date: an informal mid–year performance appraisal; and an end–of–year performance appraisal with an overall performance rating in accordance with § 7–503 of this subtitle. An employee’s performance may be rated on a performance appraisal as follows: outstanding; satisfactory; or unsatisfactory.