Pope, 21, has been drafted in as cover for Michael Ingham, sidelined due to a groin injury, and is expected to go straight into the starting line-up for Saturday's league game at Southend.
Centre-half Lowe, 28, will also be in contention for the weekend. Both players have joined for an initial month.
Pope's only appearance for Charlton to date came as a substitute on the final day of last season against Bristol City, while he has had loan spells at Cambridge and Aldershot.
Lowe has been a regular for Chelltenham this season, making 17 appearances.
Meanwhile, York defender Tom Allan has joined Harrogate Town on loan for a month. Team-mate Tom Platt spent a similar period on loan at the Skrill North side last season.