Over time, the photovoltaic cells on the ISS' existing Solar Array Wings on the
Integrated Truss Structure have degraded gradually, having been designed for a 15-year service life. This is especially noticeable with the first arrays to launch, with the P6 and P4 Trusses in 2000 and 2006. To augment the wings, three pairs of scaled-up versions known as iROSA launched in the trunks of the
SpaceX Dragon 2 cargo version from early June 2021 to early June 2023, aboard
SpaceX CRS-22,
CRS-26, and
CRS-28. A fourth pair will be launched after 2025. Work to install iROSA's support brackets on the P6 truss mast cans holding the Solar Array Wings was initiated by the crew members of
Expedition 64 in late February 2021. was successful until a spacesuit computer malfunctioned and the iROSA encountered technical problems with deployment, resulting in the spacewalk being cut short early, having lasted 7 hours and 15 minutes. Two more spacewalks, on 20 and 25 June and lasting between 6 hours 28 minutes and 6 hours 45 minutes, It was postponed to September after Vande Hei encountered "minor medical issues". He was replaced by Thomas Pesquet. The spacewalk began on 12 September 2021 and lasted 6 hours and 45 minutes. The second pair of arrays were launched aboard SpaceX CRS-26 on 26 November 2022. They completed the installation on 22 December. On 9 June 2023,
Expedition 69 crew members
Stephen Bowen and
Warren Hoburg began a spacewalk to install the arrays at their final locations, at the 1A power channel and mast can on the S4 segment, and at the 1B power channel and mast can on the S6 segment. They completed the installation on 15 June. The last pair of iROSAs, the seventh and eighth, are planned to be installed on the 2A and 3B power channels on the P4 and S6 truss segments after 2025. The
Power and Propulsion Element of
Lunar Gateway and the
Double Asteroid Redirection Test (DART) mission used ROSA technology to power its
solar electric propulsion. The ROSA on DART enabled the spacecraft to navigate through space and reach the
Didymos asteroid system. The flexible and rollable modular wings were lighter, more compact and stiffer in space and smaller than iROSA. Each array slowly unfurled to reach 28 feet (8.53 m) in length. DART was the first probe to fly the new arrays, paving the way for their use on future missions.
Redwire delivered ROSA to
APL in May 2021 and worked closely with the APL team for some weeks to carefully install them onto the spacecraft. The installation was completed on 13 August 2021. A small portion of each DART solar array is configured to demonstrate
Transformational Solar Array technology, which has very-high-efficiency SolAero Inverted Metamorphic Multijunction (IMM) solar cells and reflective
concentrators providing three times more power than current solar array technology. This ROSA technology was later extended for commercial applications, first customer being
Ovzon. Their satellite was
Maxar Technologies-built
Ovzon-3 that was successfully launched on a
Falcon 9 rocket on 3 January 2024 to a
Geostationary transfer orbit. Later, the solar arrays were deployed on 10 January 2024. ==Missions==