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Proton launch facilities in Baikonur


Proton launches Inmarsat-5 F2

During the first Russian orbital launch attempt of 2015, the 402nd Proton rocket successfully delivered the Inmarsat-5 F2 communications satellite for the London-based Inmarsat plc commercial satellite operator on February 1.

Proton lifts off with Inmarsat-5 F2 satellite on Feb. 1, 2015. Credit: ILS



Moscow time
Scheduled elapsed time
Actual elapsed time
7:31 a.m.
Stage I separation
119 seconds
-1 second
Stage II separation
Payload fairing separation
345 seconds
Stage III separation
-1 second
Briz-M firing 1 starts (for 04 min. 27 s.)
676 seconds
Briz-M firing 1 ends
939 seconds
- 4 seconds
Briz-M firing 2 starts (for 19 min. 34 s.)
6,630 seconds
Briz-M firing 2 ends
7,792 seconds
-12 seconds
Briz-M firing 3 starts (for 9 min. 24 s.)
15,829 seconds
Briz-M firing 3 ends
16,389 seconds
-4 seconds
Briz-M jettisons its external tank
16,439 seconds
-4 seconds
Briz-M firing 4 starts (for 8 min. 27 s.)
16,530 seconds
Briz-M firing 4 ends
17,030 seconds
-7 seconds
Briz-M firing 5 starts (for 3 min. 29 s.)
54,905 seconds
Briz-M firing 5 ends
55,112 seconds
-2 seconds
Spacecraft separation
55,841 seconds
-19 seconds

*February 2

Ground track, flight profile and the latest data on the Proton mission to deliver the Inmarsat-5 F2 satellite on Feb. 1, 2015. Credit: ILS

Launch profile

The Proton-M/Briz-M launch vehicle lifted off as scheduled on Feb. 1, 2015, at 15:31:00 Moscow Time (7:31 a.m. EST) from Pad 39 at Site 200 in Baikonur Cosmodrome.

The flight profile was designed to be virtually identical to the previous Proton mission with the Inmarsat-5 satellite. The 15-hour 31-minute orbital insertion process included the delivery of the satellite into the Supersynchronous Transfer Orbit with an altitude of 65,000 by 4,341 kilometers, which is almost twice as high as the satellite's ultimate destination in the geostationary orbit at 36,000 kilometers above the Equator. The satellite was to use its own propulsion system to enter an operational orbit with an orbital position 55 degrees West longitude over the Equator.

According to the GKNPTs Khrunichev, the developer of the Proton rocket, the launch sequence for the Inmarsat-5 F2 mission was to start with a traditional "Klyuch na Start" (Key to liftoff) command issued 300 seconds before a scheduled liftoff. It was followed by the KP-120s command, signaling 120 seconds to the liftoff. The readiness of the upper stage for launch was declared at T-113 seconds. Five seconds before launch, the OTP command (The completion of accurate control) was issued, followed by the Zemlya-Bort ("Ground to board") command, marking the readiness of the launch vehicle for the autonomous flight just two seconds before liftoff. At the same time, the thrust control for the rocket's first stage engines was activated and a second later, a membrane holding the supply of oxidizer into the engine was cut triggering an instantaneous ignition. The propulsion system reached an operational thrust in a second, lifting the rocket off the pad.

Following the liftoff, Proton passed the maximum dynamic pressure of the atmosphere 62.4 seconds in flight and its propulsion system entered a full-thrust mode, known as F1, at T+108 seconds. The Proton's first stage separated 119.63 seconds after the liftoff, as the second stage begins to fire its engines through a lattice structure connecting the boosters. The second stage continued firing until T+327.18 seconds and then separated with the help of small solid motors. During the operation of the third stage, the payload fairing split in two halves and dropped away 344.98 seconds after the liftoff. The third stage completed its work and separated 582.22 seconds in flight.

Three booster stages of the Proton rocket were programmed to deliver the payload section, including the Inmarsat-5 F2 and the Briz-M upper stage, into a suborbital trajectory matching an orbital inclination of 51.5 degrees toward the Equator. Briz-M then performed its first engine firing lasting almost four and a half minutes to reach an initial parking orbit at an altitude of around 173 kilometers. After making an almost full revolution, around an hour and a half later, Briz-M fired again for less than 20 minutes to boost an apogee (highest point) of its orbit to 6,000 kilometers. After a more than two hours of unpowered flight, Briz-M performed two more engine runs, this time to raise an apogee to more than 65 thousand kilometers from Earth. Since the external tank of the Briz-M stage runs out of propellant in the middle of an almost 18-minute maneuver, the firing was split into two burns separated by the jettisoning of the empty tank. The stack will then climb passively for 10.5 hours to its supersynchronous altitude.

Finally, the Briz-M ignited its main engine for three and a half minutes to enter a super-synchronous transfer orbit. The same maneuver also reduced an orbital inclination from 50.5 degrees to 26.39 degrees toward the Equator. Inmarsat-5F2 separated from Briz-M around 12.5 minutes after the completion of the fifth maneuver, just 19 seconds ahead of schedule.

Following the release of the satellite, Briz-M conducted two maneuvers with its small thrusters to enter a 2,744 by 63,522-kilometer orbit at a safe distance from its payload. The tanks onboard the stage were depressurized to avoid a potential explosion resulting in the contamination of the Earth's orbit with space junk.

According to industry sources, the Proton rocket for the Inmarsat-5 F2 mission was equipped with new Angular Velocity Sensors, DUS, replacing infamous PV-301 systems, whose wrong installation led to a spectacular crash of Proton in July 2013.

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Inmarsat-5 F2 satellite


An artist rendering of the Inmarsat-5 F2 satellite. In reality, the spacecraft would deploy its solar panels and antennas much farther from Earth than depicted here.

Based on the 702HP satellite developed by Boeing, the six-ton Inmarsat-5 (a.k.a. I-5) was conceived to form the three-satellite constellation to support Inmarsat’s Global Xpress network, also known as GX.

Global Xpress was designed to offer seamless voice and data communications around the world and deliver unprecedented mobile broadband speeds of up to 50 megabytes per second for users in the government, maritime, enterprise, energy and aeronautical sectors. Inmarsat promised to invest an estimated $1.2 billion in the Global Xpress program, which included launch costs. In October 2013, Inmarsat decided to procure the fourth I-5 satellite from Boeing also based on the 702HP platform with a completion date in the middle of 2016.

The Inmarsat-5 F2 satellite was equipped with 89 Ka-band transponders and featured six steerable spot beams to open communications channels on demand. The satellite was designed to function in the geostationary orbit at 55 degrees West longitude over the Atlantic for at least 15 years, covering the Americas and the Atlantic Ocean. The satellite will be in ideal position for providing mobile voice, data and video to airline passengers and submarine crews. Boeing also reported lending the satellite's capacity to provide secure communications across land, sea and air to unspecified US government agencies.

The satellite is equipped with a pair of five-section solar panels featuring ultra triple-junction gallium arsenide solar cells. They are projected to deliver 15 kilowatts of power at the beginning of the satellite's service, eventually degrading to no less than 13.8 kilowatts after 15 years of operation. Solar panels will charge an onboard dual lithium-ion battery.

For propulsion, the satellites based on 702HP platform come equipped with the main liquid-propellant orbit-correction engine and eight ion engines powered by xenon gas.

Known specifications for the Inmarsat-5 F2 spacecraft:

Spacecraft fueled mass
5,900 or 6,070 or 6,104 kilograms
Spacecraft dry mass
3,663 or 3,750 kilograms
Number of transponders
89 Ka-band
Main engine thrust
445 Newtons
Ion attitude control and station-keeping propulsion
Four 22-newton axial and four 10-newton radial movement thrusters
Projected life span
15 years
Power supply during the life span of the satellite
From 15 to 13.8 kilowatts
Solar array span in deployed position
33.8 meters
Dimensions in orbit
6.98 by 8.08 meters
Dimensions in folded position
6.98 by 3.59 by 3.27 meters
Orbital position
55 degrees West longitude
Spacecraft manufacturer
Boeing Space and Intelligence Systems, California, USA
Spacecraft platform
Boeing (formerly Hughes) BSS-702HP

Mission history

The agreement to launch a trio of the fifth-generation Inmarsat satellites on three Proton rockets during 2013 and 2014 was first announced on Aug. 1, 2011. The first satellite in the Inmarsat-5 series was launched on Proton on Dec. 8, 2013.

By February 2014, the launch of the second bird -- Inmarsat-5 F2 -- was planned in September of the same year, however by December, the mission was re-scheduled for Jan. 30, 2015.

Assembled by Boeing in California, the satellite left its factory in El Segundo on December 16, 2014, and arrived to Baikonur two days later. The spacecraft was first delivered to a processing building at Site 92A-50 where it was stored through Christmas holidays.

By mid-January 2015, a technical problem during the fueling of the satellite in Baikonur required to add two days to the launch processing, pushing the scheduled liftoff from January 30 to February 1. Inmarsat-5 F2 was integrated with its Briz-M upper stage on January 20.

The Proton launch vehicle with the satellite was rolled out from the assembly building on January 27 and after two days at the fueling site arrived to the launch pad at Site 200 on January 29.

Rollout of the Proton-M rocket with Inmarsat-5 F2 to launch pad.


A Proton rocket with the Inmarsat-5F2 satellite is erected onto the launch pad on January 29 in preparation for Russia's first space launch of 2015.


A Proton rocket with the Inmarsat-5 F2 satellite shortly after its rollout to the launch pad on Jan. 29, 2015.


Proton lifts off with Inmarsat-5 F2 satellite on Feb. 1, 2015. Credit: ILS



Next Proton mission: Ekspress-AM7

Read (and see) much more on the history of the Russian space program in a richly illustrated, large-format glossy edition:



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The article by Anatoly Zak

Last update: March 18, 2015

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Inmarsat-5 F2 in orbit. Credit: Boeing

Parking orbit

Artist rendering of the Inmarsat-5 F2 satellite and its Briz-M upper stage in the initial parking orbit.


Artist rendering of Briz-M's second firing.


Briz-M sheds its empty external tank between its third and fourth engine firings.


Typically for an upper stage operating in weightlessness, Briz-M first fires its small thrusters to give the vehicle initial acceleration to ensure a reliable propellant supply into the main engine during prolonged orbit correction maneuvers.


Briz-M conducts 4th orbit correction with its main engine.



Click to enlarge. Credit: Boeing


Inmarsat-5 F2 satellite (left) and F1 version on the right during their assembly in El Segundo, California. Click to enlarge. Credit: Boeing


Inmarsat-5 F2 is unloaded from Antonov-124 cargo plane in Baikonur on Dec. 18, 2014. Click to enlarge. Credit: GKNPTs Khrunichev


Inmarsat-5 F2 during its integration with the upper stage in Baikonur. Click to enlarge. Credit: GKNPTs Khrunichev


Payload section with Inmarsat-5 F2 satellite is being integrated with the Proton rocket on Jan. 20, 2015. Click to enlarge. Credit: Roskosmos


Proton with Inmarsat-5 F2 is moved from assembly bench to its transporter for the trip to the launch pad. Click to enlarge. Credit: GKNPTs Khrunichev


Proton makes a two-day stop at the fueling station on its way to the launch pad. Click to enlarge. Credit: Roskosmos


Click to enlarge. Credit: Roskosmos


Click to enlarge. Credit: Roskosmos


Rollout of the Proton rocket with Inmarsat-5 F2 satellite to the launch pad on Jan. 29, 2015. Click to enlarge. Credit: Roskosmos


Proton lifts off with Inmarsat-5 F2 satellite on Feb. 1, 2015. Credit: Roskosmos