WASHINGTON — International Launch Services says Russia’s Proton rocket will be better able to compete for constellation launches, along with other missions, thanks to new orbits accessible through an upcoming variant of the rocket.

ILS’s Proton Medium, a simplified version of the rocket that uses three stages instead of four, requires fewer drop zones for the early stages after they deplete their fuel and fall back to Earth. That reduction in drop zones means the Baikonur Cosmodrome in Kazakhstan can support missions to inclinations previously inaccessible to ILS.

“What that does from a Baikonur Cosmodrome perspective, it opens up a lot more launch azimuths that we can launch to, and specifically we can now support polar-type missions out of Baikonur with the Proton Medium,” Jim Kramer, ILS’s vice president of engineering and mission assurance, said during a March press conference.

Polar orbits are often used for Earth-observation satellites, but a number of low-Earth-orbit telecom constellations including those proposed by OneWeb, LeoSat and Telesat, feature polar-orbiting satellites. Fleet operator Iridium’s constellation as well as its second-generation Iridium Next constellation that SpaceX is launching on Falcon 9 rockets all use polar orbits as they circle the Earth for global coverage.

Those new launch trajectories enable ILS to pursue missions “where a lot of the LEO constellations want to go,” Kramer said.

ILS designed Proton Medium with parent company Khrunichev, manufacturer of Proton rockets, to be more in line with shifting commercial interests. Since announcing the variant in 2016, ILS has become increasingly confident that Proton Medium will overtake the regular Proton-M rocket in sales.

As evidence of that confidence, ILS President Kirk Pysher said the company has decided to introduce a larger 5-meter fairing on Proton Medium instead of introducing it on Proton-M, as previously planned.

“We have changed that priority now and will be introducing the 5-meter fairing first on the Proton Medium vehicle, and then we will have it on Proton-M,” Pysher said. “The 5-meter fairing is planned to launch on [Proton] Medium in the second half of 2020.”

Proton Medium’s inaugural flight is in 2019, he said.

Eutelsat said in 2016 it will be the first customer for Proton Medium for an unspecified satellite. Last month, ILS said it had secured “multiple launch assignments for Proton Medium launches” for missions that start in late 2019 from the Baikonur Cosmodrome. Pysher declined to say who booked those rockets.

Proton Medium uses an an inert interstage and longer payload fairings to maintain nearly identical dimensions to Proton-M, avoiding the need for spaceport modifications. Kramer said the 5-meter-diameter fairing is 18 meters long, providing room for bigger spacecraft or larger numbers of smallsats.

Kramer said ILS initially misjudged the lift capability of Proton Medium, and with the rocket under development now expects it will be able to lift more than 6,000 kilograms with both 4- and 5-meter fairings. Initial estimates put Proton Medium’s lift capacity between 5,000 and 5,700 kilograms, depending on the rocket’s velocity.

Pysher said Proton has four Russian federal missions this year, all Proton-M, and one commercial mission. The first Proton launch should be this spring, he said, with a Russian government satellite. ILS has a commercial mission late in the year to launch Eutelsat’s telecommunications satellite Eutelsat 5 West B and MEV-1, Orbital ATK’s first satellite-servicing Mission Extension Vehicle.