The spacecraft are probably the replacement for the Trumpet SIGINT satellites operating in a Molniya orbit. As no name is known, these are referred here as "Trumpet Follow On".
These satellite most likely use a large, unfurlable dish antenna to collect the signals. Advances in both antenna and electronics technologies have allowed for a large reduction in size compared the Trumpet predecessors.
Unlike the SDS-3 series of relay satellites, these are placed directly into the Molniya orbit, whereas the SDS-3 were placed at first in a lower interim transfer orbit.
Amateur observations show, that all three satellites were still maintaining operational orbits in 2017 and are likely still operational.
A successor to this series, the 'Trumpet-F/O-2', appeared in 2014.
Trumpet 4 (or NROL 22) carried the first SBIRS-HEO-1 early warning package. It is also the host satellite for NASA's TWINS A (Two Wide-angle Imaging Neutral-atom Spectrometers) payload, a mission of opportunity of NASA's Explorer program. The TWINS mission provides a new capability for stereoscopically imaging the magnetosphere. By imaging the charge exchange neutral atoms over a broad energy range (~1-100 keV) using two identical instruments on two widely spaced high-altitude, high-inclination spacecraft, TWINS will enable the 3-dimensional visualization and the resolution of large scale structures and dynamics within the magnetosphere. The TWINS instrument is based on the MENA instrument of the IMAGE satellite. Likely it it carried the IPS-2 (Interim Polar System) EHF communication package, which provides secure communications for the polar regions. IPS consists of a scaled-down low data rate Milstar package.
Trumpet 5 (or NROL 28) is the host for the SBIRS-HEO-2 early warning package and the TWINS B scientific package. It is also a candidate for the IPS-3 EHF communications package.
Note: The NROL designations refer to the launch, not to the payload.
|Type / Application:||SIGINT, early warning|
|Mass:||~ 3900 - 4500 kg|
|Orbit:||1111 km × 37594, 62.4° (#1); 1112 km × 37580 km, 63.6° (#2)|
|Trumpet 4 (USA 184, NROL 22, SBIRS HEO-1, TWINS A)||2006-027A||28.06.2006||Va SLC-6||Delta-4M+(4,2)|
|Trumpet 5 (USA 200, NROL 28, SBIRS HEO-2, TWINS B)||2008-010A||13.03.2008||Va SLC-3E||Atlas-5(411)|
Further high orbit SIGINT missions:
Geostationary orbit COMINT (Canyon-Chalet-Vortex-Mercury series)
Further SBIRS-High / SBIRS-Low / STSS missions: