Russia resumes GLONASS-K launches
The newest-generation satellite for the Russian GLONASS navigation constellation reached orbit after a nearly six-year hiatus. The liftoff of the Soyuz-2-1b/Fregat rocket, carrying GLONASS-K No. 15L satellite, took place as scheduled on October 25, 2020, and the spacecraft was reported to be delivered into planned orbit around 3.5 hours later.
A scale model of the GLONASS-K satellite.
GLONASS-K No. 15L mission at a glance:
A long-delayed mission
GLONASS-K No. 15L is the third satellite in the K series, the latest version in the navigation constellation. Although two previous GLONASS-K birds were launched in 2011 and 2015, a half-a-decade break had followed due to lack of components for the new-generation spacecraft, such as specialized aerospace-graded electronic units, or avionics. The shortage stemmed from the Western sanctions which banned the supply of dual-use avionics to Russia after the Kremlin's invasion of Ukraine. In response, the Russian government instituted an export-replacement program aimed at providing indigenously produced electronics for the nation's industries. The effort was complicated by the need in some cases to build entire factories virtually from scratch.
Around 2016, ISS Reshetnev, the prime developer of GLONASS satellites, began re-designing the GLONASS-K variant for the Russian-built components. It is unclear to what extent the original GLONASS-K series relied on foreign components, but the new batch of spacecraft did not come out of assembly until the end of the 2010s.
Before the end of 2019, the launch of GLONASS-K No. 15 was expected at the end of March 2020. By February 2020, the mission was planned for May and at the beginning of April, the launch was pushed to June 27, with the planned delivery of the satellite to the launch site in the middle of May 2020, RIA Novosti reported quoting unnamed sources. However, in the first half of May, the launch was postponed from June 27 to the middle of July due to delays with the manufacturing of the satellite, RIA Novosti said.
In early July, it was reported that the launch date had slipped to August 6, with the delivery of the satellite to the launch site before the end of the month. Around July 10, ISS Reshetnev released a video saying that the shipment of the spacecraft to the launch site would take place within days. However, by the end of July, the launch slipped from August 6 until the end of August 2020, RIA Novosti reported. By the middle of August, the launch was postponed again, this time until October 17, pushing it behind another Soyuz rocket mission with the Gonets-M satellites. By early October 2020, the launch was set for October 25, 2020.
On October 22, ISS Reshetnev announced that the GLONASS-K satellite had been integrated with its Soyuz-2 launch vehicle which was being prepared for the rollout to the launch pad after an approval from the State Commission overseeing the flight.
The liftoff of the Soyuz 2-1b/Fregat rocket with the third GLONASS-K satellite took place as scheduled on October 25, 2020, at 22:08:42.441 Moscow Time from Pad No. 4 at Site 43 in Plesetsk. (In case of a 24-hour delay, the launch time would be advanced to 22:04:38 Moscow Time on October 26.)
Several minutes after the fact, the Russian miliary confirmed through the official media that the pre-launch operations and the liftoff of the GLONASS-K had proceeded as planned. The assets of the Titov Chief Test Center of the Russian Air and Space Forces, VKS, began tracking the vehicle at 22:11 Moscow Time, the Ministry of Defense said.
The latest launch of GLONASS-K likely emulated the flight profile of the previous missions. Under that scenario, after several seconds of vertical ascent, the launch vehicle heads southeast to align its ground track with an orbit inclined 64.77 degrees toward the Equator. The four boosters of the first stage will separate around two minutes into the flight. Around 45 seconds later, the payload fairing protecting the satellite will be commanded to split into two halves and drop off because the vehicle will be above the discernible atmosphere by that time.
The second (core) stage of the rocket will continue firing until around 4.7 minutes into the flight, separating moments after the ignition of the RD-0124 engine on the third stage. Seconds later, the cylindrical aft section of the third stage will split into three segments and separate as well.
The third stage of the rocket will complete its powered ascent and separate from the payload section nine minutes and 22 seconds after liftoff. Flying just short of orbital velocity, the nearly empty booster will naturally reenter the Earth's atmosphere near the opposite side of the Earth from the launch site, with its flaming remnants projected to fall into the southern section of the Pacific Ocean.
Within an hour after the launch, the official TV channel of the Russian military reported that the Fregat upper stage had separated from the Soyuz-2-1b launch vehicle as planned.
Space tug maneuvers
During a typical GLONASS mission, the Fregat-M upper stage conducts three orbital maneuvers to deliver the spacecraft to its operational circular orbit more than 19,000 kilometers above the Earth's surface.
The first firing of the Fregat's main engine, lasting around 20 seconds, is initiated around a minute after the separation from the third stage. The maneuver inserts the stack into an initial parking orbit and, after a less-than-half-an-hour passive flight, the Fregat fires its main engine again, this time for around 9.5 minutes. The second maneuver stretches the original near-circular orbit, boosting its apogee (highest point) to a target altitude of more than 19,000 kilometers. The Fregat/GLONASS stack then climbs that trajectory for more than 2.5 hours before firing again. The third Fregat maneuver at apogee, lasting just under four minutes, makes the orbit circular at the newly reached altitude and it should be followed by the separation of the satellite around 30 seconds after the completion of the maneuver.
According to the flight program, the separation of the GLONASS-K No. 15 from Fregat was scheduled on October 26, 2020, at 01:40:31.564 Moscow Time (6:40 p.m. EDT on October 25). Within half an hour, the Russian military confirmed that the Fregat had successfully deployed the GLONASS-K satellite into a planned orbit.
ISS Reshetnev confirmed that all systems aboard the GLONASS-K satellite had functioned well and the spacecraft had deployed all its mechanical systems. The company's press-release said that its customer's representatives with the support of specialists at ISS Reshetnev had conducted a trial attitude control of the spacecraft and began testing its onboard systems.
Upon the release of the satellite, Fregat is usually programmed to conduct two maneuvers with its attitude-control thrusters, SOZ, to enter a burial orbit above its former satellite passenger. The Russian military announced that these maneuvers had taken place.
Several hours after the launch, the US Space Command, USSPACECOM, listed orbital elements for two objects associated with the launch in orbit with an inclination around 64.8 degrees toward the Equator. The first appeared to be a satellite in a 19,120 by 19,151-kilometer orbit, while the second object in a 19,141 by 19,521-kilometer orbit was probably a Fregat upper stage detected after it had maneuvered away from the satellite to a higher burial orbit:
According to the original plans, GLONASS-K No. 15 (System No. 705) was supposed to replace the old GLONASS-M satellite with system No. 723 launched in 2007. But in November 2020, the GLONASS-M No. 53 (System No. 753) failed in orbit due to depressurization of its main body, two years ahead of its official warranty. As a result, plans were made to replace the lost spacecraft with GLONASS-K No. 705.
GLONASS-K satellite during pre-launch processing circa 2020. Credit: ISS Reshetnev
A Soyuz-2-1b rocket with GLONASS-K No. 15 is ready to leave the vehicle assembly building in Plesetsk. Click to enlarge. Credit: Russian Ministry of Defense
A Soyuz-2-1b rocket with GLONASS-K No. 15 satellite rolls out to the launch pad in Plesetsk. Click to enlarge. Credit: Russian Ministry of Defense
A Soyuz-2-1b rocket with GLONASS-K No. 15 arrives at the launch pad on October 22, 2020. Click to enlarge. Credit: Russian Ministry of Defense
Click to enlarge. Credit: Russian Ministry of Defense
A Soyuz-2-1b rocket with GLONASS-K No. 15 satellite is being installed on the launch pad in Plesetsk. Click to enlarge. Credit: Russian Ministry of Defense
A Soyuz-2-1b rocket with GLONASS-K No. 15 satellite shortly after its rollout on the launch pad in Plesetsk on Oct. 22, 2020. Click to enlarge. Credit: Russian Ministry of Defense
A Soyuz-2-1b rocket with GLONASS-K No. 15 satellite lifts off on October 25, 2020. Click to enlarge. Credit: Russian Ministry of Defense