SpaceX preparing to launch third GPS Block III satellite

SpaceX is readying their Falcon 9 rocket to launch the third Block III Global Positioning System (GPS) satellite, named SV03. Block III is the next generation of GPS satellites, replacing the aging Block II series. This will be SpaceX’s second GPS launch, out of the five they have been awarded so far. SV03 is scheduled to launch from SLC-40 at Cape Canaveral Space Force Station at 3:55 PM ET on June 30.

SV03 Launch

SpaceX previously launched the maiden GPS Block III satellite, SV01, on a Falcon 9 in December 2018. SV01 was the first launch contract that SpaceX won in the Evolved Expendable Launch Vehicle (EELV) program.

In March 2017, SpaceX beat United Launch Alliance (ULA) to secure the launch contract for the third Block III satellite, SV03. At that time, the launch of SV03 was expected in early 2019.

Although SV01 and SV03 have flown or will fly on a Falcon 9 Block 5, their mission profiles will be slightly different.

For SV01’s launch, the Air Force requested that the Falcon 9 fly in an expendable configuration to dedicate more performance to the satellite. This meant that the first stage – the new core B1054 – had to be expended on its first flight.

For SV03, however, the Space Force – who now run the GPS program – gave SpaceX the go-ahead to set aside some vehicle performance to enable first stage recovery.

Because of the satellite’s deployment orbit and relatively high mass – 3.9 metric tons – the first stage will perform a ballistic landing. This will take place approximately 634km downrange, on SpaceX’s droneship Just Read The Instructions.

The exact deployment orbit for SV03 has not been publicized as of writing. However, if it follows a similar profile to SV01, it would be deployed into an approximately 1,200 by 20,000km transfer orbit. From there, the satellite would maneuver itself into a 20,200km circular orbit.

On July 25, SpaceX crews rolled the Falcon 9 stack – minus SV03 and its fairing – onto SLC-40 to perform a static fire test.

A static fire test is a complete dress rehearsal of almost all launch day activities – including propellant loading and a brief test fire of the nine first stage engines. SpaceX later confirmed that the test was nominal and that they were on track for the launch.

The second stage for this mission features a gray band of paint covering the second stage’s RP-1 tank. The gray stripe is used on longer-duration missions – such as SV03 – because the second stage will perform a long coast between engine burns. For SV03 specifically, the second stage will coast for nearly an hour between its two engine firings.

The extreme environment of space can dramatically alter the propellant’s temperature, affecting engine performance. The gray band’s darker color warms the RP-1 by absorbing solar radiation, ensuring that the fuel does not freeze.

The gray stripe was tested on the CRS-18 mission in August 2019, where the second stage performed a long coast after Dragon separation.

SV03’s Falcon 9 also features first stage B1060, making its debut flight. Should its landing be successful, B1060 will be refurbished and made available for a second flight.

Due to past landing failures, SpaceX has had few boosters to use for launches of their Starlink internet satellites. The addition of B1060 to the mix will help in their ramping up of launches.

On launch day, the Falcon 9 will lift off from SLC-40 and begin pitching downrange. Due to the high inclination orbits the GPS satellites use – 55 degrees – the rocket will head northeast from Cape Canaveral.

At T+2 minutes 35 seconds, the first stage engines will shut down – 9 seconds earlier than on SV01. The two stages will separate, and the second stage’s single Merlin 1D Vacuum engine will ignite at T+2:42. The two fairing halves will separate at T+3:38 and descend to their own recovery zone.

SpaceX’s twin fairing recovery vessels GO Ms. Tree and GO Ms. Chief are positioned in the Atlantic Ocean to attempt to catch one faring half each in their nets approximately 45 minutes after launch. If they miss their catch, crews can recover the fairings out of the water.

The second stage will continue firing until its engine shuts down at T+8:07. From that point it will coast for nearly an hour until it reignites for a 45-second burn at T+1:03:28.

GPS SV03 will be deployed at T+1:29:14 – marking the end of the mission.

GPS Block III

As its name suggests, GPS Block III will be the third major version of the GPS satellites.

The Department of Defense started the GPS program in 1973. In 1978, the first of eleven prototype satellites were launched. These satellites – referred to as Block I – were meant to prove the concept and develop technologies for the future operational GPS constellation.

The Block I series satellites were only expected to last five years on orbit. However, the final Block I satellite was in service for just over 10 years, being retired in November 1995.

GPS Block II was intended to become the first operational series in the program, building off developments made throughout the Block I series. The Block II satellites feature two rubidium and two cesium atomic clocks, which the satellites use to help accurately determine user location.

Block II itself had five series of spacecraft – II, IIA, IIR, IIR-M, and IIF. Each series boasted several upgrades over the previous, often involving new signals or increased autonomous operations.

Rendering of a GPS Block IIF satellite in orbit. Credit: U.S. Air Force

The final Block II satellite launched in 2016. Many are still in operation or in reserve and will be slowly phased out as Block III becomes operational.

Block III offers enhanced position accuracy and more powerful signals – enabling higher availability and throughput. The spacecraft in the series are built on Lockheed Martin’s A2100 bus – the same used by NOAA’s GOES-R-series weather satellites.

The maiden launch of Block III was expected to take place in 2014. However, delays in the program led to the launch being pushed back to late 2018.

Initially, United Launch Alliance was contracted to launch the first Block III mission, SV01, with SpaceX flying the second, SV02. in 2017, the Air Force swapped the missions – giving SpaceX the maiden Block III launch.

SpaceX launched SV01 in December 2018 on an expendable Falcon 9 Block 5. ULA launched SV02 in August 2019 on the final Delta IV Medium flight.

SpaceX was additionally contracted to launch satellites SV03-06 throughout 2020 and 2021.

The 10 Block III satellites will be joined by 22 Block III follow-on, or IIIF, satellites. Block IIIF will bring new capabilities to the Block III design over time in what are called “Technology Insertion Points”. These four points are earmarked as the only times when new technology can be added to the satellite design. These are expected to take place around 2026, 2028, 2030, and 2033.

Block IIIF launches will take place between 2026 and 2034.

The next flight for SpaceX will be the 9th operational Starlink mission, currently scheduled for July.

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