The third SpaceX commercial cargo mission to the International Space Station has been delayed until no earlier than March 30 because of payload contamination that may require some new parts to be installed.

Originally set for March 16, the Falcon 9 launch was delayed on March 14 to “ensure the highest possible level of mission assurance and allow additional time to resolve remaining open items,” according to a NASA update that quoted SpaceX and referred additional questions to the Hawthorne, Calif., commercial-cargo launch service provider.

Sam Scimemi, the ISS director in the Human Exploration and Operations mission directorate at NASA headquarters, elaborated later that day during a panel discussion on the ISS sponsored by the Space Transportation Association.

“We’ve had some issues with payload contamination that we will be addressing,” he said. “We’re going to have to assess that and replace some parts and get the rocket ready for launch again. Our current launch date right now I believe is March 30.”

SpaceX and NASA did not answer questions about the exact source and nature of the contamination on March 17, or about what payloads may be contaminated. A NASA ISS status blog posted on March 13 said the launch would be delayed because of unspecified “contamination found on the beta cloth shields in the SpaceX-3 unpressurized external trunk,” and noted that “[s]pecialists are reviewing options for addressing the contamination on the beta cloth shields.”

Beta cloth is a special fabric typically used in multi-layer insulation for thermal protection in space and to shield orbiting spacecraft against the corrosive effects of atomic oxygen. One of the payloads in the SpaceX Dragon’s unpressurized “trunk” is the Optical Payload for Lasercomm Science (Opals), a communications testbed developed and built at the Jet Propulsion Laboratory that is designed to study high-data-rate communications between space and the ground using laser light.

The experiment is mounted on a standard ISS flight releasable attachment mechanism (FRAM), and includes a laser, off-the-shelf avionics and a custom power board in a container pressurized with air at 1 atmosphere. Mounted on the Fram outside the protective container is a gimbaled optical device that includes an uplink camera and a laser collimator to narrow the laser beam on the downlink. Both would be susceptible to contamination.

Also in the unpressurized trunk, and susceptible to contamination, are four off-the-shelf, high-definition cameras that will be mounted outside the station as the High Definition Earth Viewing (HDEV) experiment. HDEV is protected against space temperatures but not the radiation that affects its cameras’ detectors, which will allow engineers to determine which commercial cameras work best in space for live online video streaming.