SpaceX Falcon 9 lofts three Canadian radar satellites

by William Graham

SpaceX deployed Canada’s Radarsat Constellation via a Falcon 9 launch Wednesday. Lifting off from California’s Vandenberg Air Force base at 07:17 Pacific Time (14:17 UTC), Falcon delivered the three radar-imaging satellites to orbit a little over an hour after launch.

(Lead photo by Sam Sun for NSF/L2 – full set in L2, here)

The Radarsat Constellation Mission (RCM) is the successor to the Canadian Space Agency’s Radarsat-2 satellite, marking the start of a third generation for Canada’s radar imaging satellite systems. While Radarsat-2 and the earlier Radarsat-1 were single-satellite missions, Radarsat Constellation uses three spacecraft to increase the frequency of coverage and enable new applications for the data the satellites gather.

Falcon 9 sent all three satellites into orbit with a single launch on Wednesday.

Like the earlier Radarsat spacecraft, each RCM satellite carries a C-band synthetic aperture radar (SAR) payload. A deployable antenna on the nadir – or Earth-facing – side of the satellite transmits signals towards the surface which are reflected back. By listening for these echoes and processing the results, the spacecraft can begin to build a profile of the ground below it. SAR imaging allows satellites to make observations of the Earth’s surface day or night, and in any weather conditions, whereas visual imaging techniques require clear skies and sunlight.

Images taken by the Radarsat Constellation will support a range of applications including national defense ecological and disaster monitoring and maritime surveillance. Many of these missions are already undertaken by Radarsat-2, but with three spacecraft RCM will be able to make daily observations often at higher resolutions than its predecessor.

The satellites will map sea ice in the North Atlantic, Arctic and the Great Lakes to support ship navigation, track ships in areas of interest to Canada’s Department of National Defense, monitor changes in Canada’s coastal regions, forests and wetlands and collect data to aid with crop management.

Another application will be to collect images following disasters – particularly flooding, storms and earthquakes – that will help the emergency services plan their response and manage the situations. RCM will also help to detect and monitor oil spills, tracking pollution and aiding efforts to combat it.

RADARSAT during payload integration work – via CSA

The radar imaging payloads aboard the RCM satellites operate in the C-band of the electromagnetic spectrum, at frequencies around 5.4 gigahertz. It can produce images at resolutions between 5 and 50 meters (16 and 164 feet) with respective swath widths of 20 to 350 kilometers (12 to 218 miles, 11 to 189 nautical miles). In addition to its SAR payload, each satellite carries four Automatic Identification System (AIS) receivers to pick up tracking and identification signals from transponders mounted aboard ships. This will help to relay tracking data for vessels out of range of the shore, helping to keep mariners safe at sea.

Planning for the Radarsat Constellation Mission began in 2004 – before Radarsat-2 had launched – when an initial proposal was made to the Cabinet of the Canadian Government. Over the next few years, the Canadian Space Agency worked to identify its requirements for the spacecraft, leading to a preliminary mission design which was completed in March 2010. This was refined into the mission’s final design, with construction of the satellites beginning in January 2013. Following extensive testing on the ground, the three spacecraft were transported to the launch site in the third quarter of 2018.

The three identical satellites that make up the Radarsat Constellation were built by MacDonald, Dettwiler and Associates (MDA Corporation), a Vancouver-based aerospace contractor that is a subsidiary of Colorado’s Maxar Technologies. Constructed around a SmallSAT MAC-200 platform developed by Bristol Aerospace, each spacecraft has a mass of 1,430 kilograms (3,150 lb). Each satellite measures 1.1 by 1.1 by 3.6 meters (3.6 by 3.6 by 11.8 feet), with the radar antenna having a span of 6.98 meters (22.9 feet).

The RCM satellites are expected to operate for at least seven years. However, the Canadian Space Agency will be hoping that they follow their predecessors in surpassing their original design parameters.

Canada’s first radar imaging satellite, Radarsat-1, was launched aboard a Delta II rocket on 4 November 1995 with an anticipated five-year service life. The satellite exceeded its design life by over twelve years, finally ceasing operations following a malfunction in March 2013. Its replacement, Radarsat-2, had been launched in December 2007 by a Russian Soyuz-FG/Fregat rocket and was designed for seven-and-a-quarter years of service. At the time of Radarsat Constellation’s launch, Radarsat 2 remains in service and is expected to operate alongside the new satellites for as long as it is able to do so.

The launch of the Radarsat Constellation Mission was the second major mission that SpaceX has undertaken for the Canadian Space Agency: SpaceX previously carried CSA’s multipurpose CASSIOPE satellite in September 2013 on the sixth Falcon 9 mission.

The CASSIOPE launch was the maiden flight of the Falcon 9 v1.1, an upgrade over the original Falcon 9 design that has since been superseded by the Full Thrust or v1.2 model and the Block 5 rockets that are now being flown. It was also SpaceX’s first launch from Vandenberg Air Force Base, the first Falcon 9 to fly with a payload fairing, and CASSIOPE was the first payload launched by Falcon 9 other than SpaceX’s Dragon spacecraft.

Nearly six years on from the CASSIOPE launch, deployment of the RCM satellites was Falcon 9’s seventy-second launch – not including two flights of the derived Falcon Heavy vehicle. In that time SpaceX has also achieved their ambition of making Falcon 9’s first stage reusable: the booster that propels RCM off of its launch pad on Wednesday was making its second flight.

The booster in question – Core 1051.2 – was first flown in March as part of the rocket that carried the Crew Dragon spacecraft into orbit for its successful uncrewed DM-1 demonstration mission.

B1051 ahead of launching the DM-1 mission – by Brady Kenniston for NSF/L2

RCM was launched by a Block 5 Falcon 9, a version of the rocket introduced last May as the ultimate result of incremental upgrades that SpaceX had made to the rocket over the previous eight years. Block 5 is designed to facilitate rapid reuse of recovered stages for multiple missions, and froze the design so it could be human-rated for NASA’s Commercial Crew program.

Recovery of Falcon’s first stage is achieved by a series of engine burns performed after separation from the rocket’s second stage, which carries the rocket’s payload the rest of the way to orbit, culminating with a powered vertical landing.

Depending on the mass of its payload and the amount of energy required to reach its target orbit, the booster can either fly back to a landing pad at the launch site (a return-to-launch-site, or RTLS, profile) or continue along its course and land aboard an Autonomous Spaceport Drone Ship (ASDS) positioned out at sea.

Following Wednesday’s launch the booster returned to Landing Zone 4 (LZ-4) at Vandenberg Air Force Base.

MAXAR image of SLC-4E and LZ-4

Landing Zone 4 was built on the site of Space Launch Complex 4W (SLC-4W), a launch pad at Vandenberg Air Force Base that was previously serviced Atlas-Agena, Titan IIIB and Titan II(23)G rockets. Part of the same complex as Falcon 9’s launch pad, Space Launch Complex 4E, SLC-4W was originally built as Launch Complex 2-3 of the US Navy’s Point Arguello launch facility in the early 1960s and supported its first launch in July 1963. Point Arguello was merged into Vandenberg Air Force Base in July 1964.

The ninety-third and last launch from SLC-4W took place in October 2003, with the final Titan II rocket deploying a weather satellite for the Defense Meteorological Satellite Program (DMSP).

The launch pad, SLC-4E, also started life as part of the Point Arguello naval facility, designated Launch Complex 2-4, however it did not see its first launch until a few weeks after the Vandenberg merger, with an August 1964 Atlas-Agena launch carrying a KH-7 GAMBIT reconnaissance satellite to orbit.

SLC-4E was later used by the larger members of the Titan family, beginning with the Titan IIID, followed by the Titan III(34)D and Titan IV, which made the last-ever Titan launch from the complex in October 2005. Prior to the commencement of Falcon 9 launches in 2013, the complex had been used for twenty-seven Atlas-Agena missions, twenty-two Titan IIID launches, seven flights of the Titan III(34)D and twelve of the Titan IV.

Vandenberg Air Force Base is located on California’s coast near the town of Lompoc, to the northwest of Los Angeles where SpaceX is headquartered. Wednesday’s launch was the fifteenth Falcon 9 launch from Space Launch Complex 4E, and the second to attempt a landing at LZ-4.

The two-stage Falcon 9 is assembled horizontally in a hangar close to its launch pad. A Transporter-Erector, known as the Strongback, is used to transport the rocket into position and raise it to vertical. The strongback also hosts umbilical connections to the Falcon 9 that facilitate fuelling, electrical and data transmission and climate control while the rocket remains on its launch pad.

Following a successful static fire on Saturday, when the countdown was rehearsed and Falcon’s first stage engines were briefly test-fired, the rocket was returned to the hangar for mating with its payload.

After rolling out with RCM aboard, Falcon was once again raised to the vertical to begin the final preparations for Wednesday’s launch. Loading of propellant into both stages of the rocket began thirty-five minutes ahead of the planned liftoff, with loading of oxidizer – liquid oxygen – into the first stage tanks commencing at the same time.

Liquid oxygen loading onto the second stage began later, at the sixteen-minute mark in the count. Both stages of the Falcon 9 burn RP-1 propellant – rocket grade kerosene, oxidized by supercooled liquid oxygen. Because liquid oxygen boils off at ambient temperatures, the rocket’s oxidizer tanks continued to be topped off until the final minutes of the countdown.

About seven minutes before liftoff the process of chilling the first stage engines down started. This prepares the fuel lines and engines for startup, when liquid oxygen at cryogenic temperatures will flow in to begin the combustion process. A few minutes later the arms at the top of the Strongback opened and the structure rotated into its launch position. The Strongback used at SLC-4E is of an older design than those used at the East Coast launch pads, and as such it is fully retracted to the launch position at this point in the countdown, instead of using the two-stage process employed at the other complexes.

The final minute of the countdown saw Falcon’s onboard computers carry out their final checks of the vehicle, while propellant tanks were pressurized and the launch pad water deluge system was activated. Forty-five seconds ahead of liftoff the Launch Director gave a final “go” for launch, and the nine Merlin-1D first-stage engines ignited at the T-3 second mark. When the countdown reached zero Falcon 9 lifted off to begin its journey with RCM.

Following a south-south-westerly track from Vandenberg, Falcon passed through the area of maximum aerodynamic pressure, or Max-Q, sixty-three seconds into flight. This is the point during ascent at which the rocket experiences the greatest mechanical stress or load, as a result of its increasing velocity. As the rocket climbs the outside air density decreases, reducing loads past Max-Q even as the rocket continues to accelerate.

Two minutes and thirteen seconds into flight, Falcon 9 reached Main Engine Cutoff, or MECO. The first stage engines shut down and four seconds later the first and second stages separated. Seven seconds after staging, Falcon’s second stage ignited to begin the first of its two planned burns. The second stage is powered by a single Merlin-1D engine which has been modified for optimal performance in the vacuum of space. This Merlin Vacuum (MVac) engine powered RCM the rest of the way into orbit.

Having protected the RCM satellites while Falcon 9 climbed through the atmosphere, the payload fairing was no longer needed after the rocket reaches space. Twenty-five seconds after second stage ignition, the fairing was jettisoned, splitting into two halves that will fall back to Earth. While SpaceX has recently been experimenting with attempts to recover the payload fairing, no such attempt – at least involving Mr. Steven – was taken during Wednesday’s launch as that ship is now located on the East Coast.

The second stage’s first burn lasted six minutes and four seconds, placing the upper stage and payload into an initial parking orbit. While this burn was ongoing the first stage – Core 1051.2 – performed the sequence of maneuvers necessary to return itself to Earth.

After separating the core reoriented itself so that its engines were pointing downrange, before beginning a boostback burn with three engines to reverse its direction of travel. This burn was complete by the three-minute, 18 second mark in the flight – sixty-one seconds after stage separation. It then changed its orientation again, ensuring that it re-enters the atmosphere engines-first.

Before re-entry, the stage deployed grid fins helped to stabilize and guide its descent. At six minutes and four seconds mission elapsed time three of the first stage engines restarted for an entry burn, reducing speed to limit heating as the stage passes back into the denser regions of the atmosphere. The final landing burn, using just the center engine, commenced as the stage approached Landing Zone 4, with touchdown seven minutes and 53 seconds after liftoff.

By recovering and reusing the first stage of its Falcon 9 rocket, SpaceX aims to reduce the cost of access to space. Although a successful landing is beneficial to SpaceX, the outcome of the first stage landing attempt had no bearing on the overall success or failure of Wednesday’s mission, whose sole objective is the delivery of the three RCM satellites into their prescribed orbit.

This was accomplished with a second burn of the second stage, following a 41-minute, 40-second coast phase. The second stage restart came fifty minutes and eight seconds into the flight, with the burn lasting just four seconds.

The Radarsat Constellation was deployed into a circular sun-synchronous orbit (SSO) at an altitude of 592 kilometers (368 miles, 320 nautical miles) and an inclination of 97.7 degrees. The first satellite, RCM-1, was deployed four minutes and 31 seconds after the second burn concludes, with RCM-2 separating three minutes and 41 seconds later and RCM-3 three minutes and 49 seconds after that.

Following deployment, the satellites will begin on-orbit testing and commissioning, with regular operations expected to begin in the last quarter of this year.

After successfully deploying its payloads the second stage will make one further burn to deorbit itself, with reentry expected over the Pacific Ocean, to the west of California, during its second orbit.

Wednesday’s launch was the seventh launch of 2019 for SpaceX – six of which have been made by Falcon 9 vehicles and the seventh by Falcon Heavy.

The next launch is currently expected to be another Falcon Heavy flight, which is slated for the end of June with a cluster of payloads under the Space Test Program’s STP-2 mission. Falcon 9’s next mission is expected in mid-July with a Dragon spacecraft on the CRS-18 resupply flight to the International Space Station.

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