Paz Radar-Imaging Satellite Heads to Polar Orbit, Mr. Steven Attempts Fairing Recovery

Four launches within the first eight weeks of the year is an impressive accomplishment, as SpaceX successfully lofted Spain’s Paz civil/military radar-imaging satellite into low-Earth orbit, earlier today (Thursday, 22 February), from Space Launch Complex (SLC)-4E at Vandenberg Air Force Base, Calif. Liftoff of the Upgraded Falcon 9 occurred on time at 6:17 a.m. PST. Following a spectacular 2017, which saw 18 launches from the East and West Coasts, 2018 has begun in fine fashion, with the maiden voyage of the long-awaited Falcon Heavy and the successful delivery of the SES-16/GovSat-1 communications satellite last month, together with the secretive Zuma payload for an undisclosed U.S. Government entity, the exact fate of which will likely remain undisclosed. As intended, the reused first stage of today’s booster—the last of the Block 3 variant of the Upgraded Falcon 9, which previously saw service on last August’s Formosat-5 mission—had been stripped of its landing legs and was not recovered.

Significantly, although the first stage was not intended to be salvaged, today’s launch was followed closely by an ocean-going vessel: in this case, a SpaceX high-speed craft, nicknamed “Mr. Steven”. Equipped with a large clawed net, which SpaceX CEO Elon Musk had earlier likened to “a giant catcher’s mitt”, it was hoped that Mr. Steven would capture the descending payload fairing from Paz, potentially saving around $6 million and increasing the likelihood of reusing this hardware on future launches. This approximate figure, quoted by numerous news outlets, is reportedly due to the estimate that the fairing costs about 10% of the price of an Upgraded Falcon 9 vehicle.

Built in 2015, the 201.7-foot-long (61.5-meter) Mr. Steven was stationed offshore in the Pacific Ocean, about 400 miles (640 km) southwest of Vandenberg. Today’s effort to bring the payload fairing safely back to Earth followed a previously successful attempt, during the SES-10 launch in March 2017. Remarkably, the fairing survived, but missed Mr. Steven. “Missed by a few hundred meters, but fairing landed intact in water,” Mr. Musk tweeted later. “Should be able to catch it with slightly bigger chutes to slow down descent.”

SLC-4E has a chequered history, having already supported 75 launches over more than five decades. First used in August 1964, the mountain-ringed pad was originally known as “PALC2-4” and supported 27 Atlas-Agena flights, through June 1967, delivering a network of KH-7 reconnaissance satellites to orbit. It re-entered service four years later and 22 Titan IIID boosters roared aloft from the newly-renamed SLC-4E between June 1971 and November 1982, launching KH-9 and KH-11 reconnaissance satellites, after which its next resident was the Titan 34D. This vehicle launched seven times from June 1983 to November 1988, including a spectacular solid-rocket motor failure and explosion in April 1986, only a few weeks after the Challenger tragedy. More recently, SLC-4E supported the final generation of Titan rockets—the Titan IV—and 12 missions were staged between March 1991 and October 2005, pushing the pad’s tally to 68 launches. Following extensive upgrades in the 2011-2013 timeframe, SpaceX staged its first Falcon 9 launch from SLC-4E in September 2013. Since then, a further six launches have occurred, most recently the fourth batch of Iridium NEXT satellites in December of last year.

Formerly called Satélite Español de Observación SAR (SEOSAR), Paz will be operated as part of an on-orbit “constellation” of Synthetic Aperture Radar (SAR) imaging platforms, which includes Germany’s TerraSAR-X and TanDEM-X satellites. Launched in June 2007 and June 2010, respectively, these two polar-orbiting spacecraft provide an imaging resolution of just 3.3 feet (1 meter) and have contributed significantly to 2D and 3D topographical mapping, surface movement, land-cover and land-use analyses, emergency response to natural disasters, environmental monitoring and defense and security applications. The two satellites fly in tightly controlled formation, at a distance ranging from 820 feet (250 meters) to 1,640 feet (500 meters), at an altitude of around 320 miles (515 km). When it reaches orbit, Paz will occupy the same orbit. It is expected that having three satellites operating together will reduce revisit times to specific locations and increasing radar-acquisition capacity.

Built by Airbus Defence and Space under a November 2008 contract with Madrid-based satellite servicers operator Hisdesat, Paz—whose name means “peace” in Spanish—weighs 3,000 pounds (1,400 kg) and is targeted to meet the security and defense requirements of the Spanish Government. As a dual-use, civil/defense mission, it will perform global observations in support of military and civilian applications, including rescue, maritime surveillance, tactical support, border control, disaster management, environmental control, risk management and counter-piracy, particularly off Somalia.

The $180 million satellite passed its Critical Design Review in April 2013 and was structurally integrated by the fall of that year. Physically, Paz consists of a hexagonal “bus” and stands 16.4 feet (5 meters) high and 8 feet (2.4 meters) in diameter, with a triple-junction gallium-arsenide solar array and lithium-ion batteries capable of generating up to 850 watts of electrical power. Three sides of the bus are occupied by electronics, another by the solar array and a fifth to house telemetry, tracking and command equipment. The final face of Paz carries the X-band SAR instrument, which measures 15.7 feet (4.8 meters) long and 2.3 feet (0.7 meters) wide and, in flight, will be oriented 33.8 degrees off-nadir. The SAR operates in multiple modes to produce radar images with variable swath width between 3 miles (5 km) and 62 miles (100 km) and resolutions between 3.3 feet (1 meter) and 50 feet (15 meters). A deployable, 10-foot (3.3-meter) boom will hold an antenna for transmission of imaging data to the ground stations at Torrejón, near Madrid, and Maspalomas, on the island of Gran Canaria, at 300 megabits per second. Finally, a Laser Retro-Reflector (LRR) will provide precise orbit-determination parameters.

Additional payloads aboard Paz include Radio Occultation and Heavy Precipitation (ROHP), which will fill a predicted gap in the availability of radio-occultation sensors for global weather and climate observations and forecasting. ROHP was formally approved for addition to the Paz payload by the Spanish Ministry of Science and Innovation, back in 2009. Also aboard the satellite is the exactEarth Automatic Ship Identification (AIS), which will provide the first-ever advanced AIS/SAR data-fusion capability for maritime surveillance from low-Earth orbit.

Initially, Hisdesat contracted with International Space Company (ISC) Kosmotras to loft Paz, atop its three-stage Dnepr booster, with launch targeted for early 2015. This would enable the satellite to be fully integrated into the network with TerraSAR-X and TanDEM-X by the fourth quarter of 2015. However, due to difficulties securing Russian Government approval to launch the Dnepr—which produced a lengthy launch delay—Hisdesat canceled the contract in July 2016 and in March of the following year a deal was reached with SpaceX, whereupon Paz would “ride-share” an Upgraded Falcon 9. Space News reported that Hisdesat had turned to the International Court of Arbitration in Paris, seeking to recover $16 million in lost launch fees from ISC Kosmotras.

In the meantime, the satellite was placed into storage, targeting a revised launch in the fall of 2017, which eventually slipped into the first quarter of the following year. Paz was shipped from Airbus’ facility in Friedrichshafen, Germany, to its Madrid-Barajas site, where the SAR sensor had been fabricated, for final integration. Last December, the satellite and its ground support equipment left Madrid and was transported by a convoy of three trucks to the Spanish Air Force Base in Torrejón de Ardóz, from whence it was flown to Vandenberg. Accompanying Paz was a 15-strong team of Airbus technicians and engineers, responsible for assembling test systems, batteries and a bespoke payload adapter to integrate the satellite with the bullet-shaped fairing of the Upgraded Falcon 9.

By this point, launch was expected at the end of January, but moved firstly until 10 February and later the 17th, with an instantaneous “window” at 6:17 a.m. PST. Last weekend, the 230-foot-tall (70-meter) booster—minus Paz—was rolled out from the horizontal integration facility and raised to the vertical on SLC-4E for a customary Static Fire Test of its nine Merlin 1D+ first-stage engines. “Static Fire Test complete,” SpaceX tweeted. “Targeting February 17 launch of Paz.” The Upgraded Falcon 9 was then returned to the hangar for integration of Paz. “The 30th Space Wing is ready to support the first West Coast SpaceX launch of 2018,” said Col. Greg Wood, who serves as vice commander of the 30th Space Wing at Vandenberg. “Each launch marks the culimination of hard work and dedication of Team V. We are excited to support this mission, as we continue to provide safe, secure access to polar orbit.”

However, on Thursday evening, SpaceX announced a 24-hour delay from Saturday morning until Sunday morning, with a revised T-0 of 6:16 a.m. PST. “Now targeting February 18 launch of Paz from SLC-4E to allow for additional time for pre-launch systems checks,” it was revealed. “Falcon 9 and payload remain healthy.” By Saturday evening, a further delay until Wednesday, 21 February, had been announced. “Team at Vandenberg is taking additional time to perform final checkouts of upgraded fairing,” SpaceX tweeted. “Payload and vehicle remain healthy. Due to mission requirements, now targeting February 21 launch of Paz.” The delay appears to have been a relatively quickfire one, for AmericaSpace tweeted Saturday that, within a matter of hours, the Upgraded Falcon 9 was rolled out to SLC-4E, then rolled back under cover in the horizontal integration facility. The booster was returned back to vertical at the pad on Tuesday afternoon.

Pressing into Wednesday, the loading of the rocket with liquid oxygen and a highly refined form of kerosene, known as “RP-1”, got underway in the pre-dawn hours, just after 5 a.m. PST. Weather conditions were predicted to be 90-percent favorable, tempered by a slight possibility of violating the rules pertaining to Ground Winds. However, as the countdown proceeded, it was Upper Level Winds which appeared out of normal constraints. According to NASASpaceflight.com, winds were at 101.8 percent of the maximum allowable limit, with an expectation that if they dropped below 100 percent, the readiness level would change from “Red” to “Green”. In the hope that the upper-level winds might subside in time for the instantaneous T-0, fueling of liquid oxygen got underway at 5:42 a.m. PST, some 35 minutes before launch time.

However, the weather was not on SpaceX’s side and a scrub was called a little after 6 a.m. “High-altitude wind shear data shows a probable 2% load exceedance,” tweeted Mr. Musk. “Small, but better to be paranoid. Postponing launch to tomorrow, assuming winds are better then.”

Realigned to a Thursday launch attempt, with an instantaneous T-0 also at 6:17 a.m. PST, the second effort to get Paz into space seemed charmed by comparison. At 6:07 a.m., as the countdown passed T-10 minutes, the terminal autosequencer was initiated and the nine Merlin 1D+ engines were chilled, ahead of ignition. At T-2 minutes, the Air Force Range Safety Officer verified that all ground-side assets were “Go for Launch” and the vehicle transitioned to Internal Power and assumed primary command of all critical functions, entering “Startup” at T-1 minute. Three seconds before launch, the Merlins thundered to life, ramping up to a combined impulse of 1.5 million pounds (680,000 kg). The stack departed SLC-4E precisely on time, at 6:17 a.m., just 22 minutes before local sunrise, offering a spectacular view to observers around Vandenberg.

Heading in a southerly direction, the first stage provided the muscle for 2.5 minutes, before separating. Next came the ignition of the Merlin 1D+ Vacuum engine of the Upgraded Falcon 9’s second stage, which ignited for a single, six-minute “burn” to place Paz into its proscribed Sun-synchronous, dawn-to-dusk orbit, at an altitude of 319 miles (514 km). The satellite was deployed at 11 minutes into the flight. When operational, after a six-month commissioning phase, Paz will be capable of transmitting over a hundred SAR images daily and store up to 256 gigabits of data in its on-board recorders. Its sensors can image up to 115,800 square miles (300,000 square km) of terrain daily and revisit the same site on Earth every 11 days.

During the early part of second-stage flight, the Upgraded Falcon 9’s payload fairing was discarded, although on this occasion not with the intent of disposing in the ocean. Instead, a SpaceX high-speed boat, nicknamed “Mr. Steven”, was equipped with a large netted “claw”, in the attempt to recover the $6 million fairing. At the post-flight press conference after the 6 February Falcon Heavy launch, SpaceX CEO Elon Musk likened it to “a giant catcher’s mitt, in boat-form”. Although today’s fairing missed Mr. Steven “by a few hundred meters”, it nevertheless survived the descent and splashdown in the Pacific Ocean and it is expected that it can be caught “with slightly bigger chutes to slow down descent” on future missions. Responding to one tweeted question, Mr. Musk noted that another fairing recovery attempt by Mr. Steven would be made in “about a month”.

Less well-covered were the additional payloads aboard the booster, which took the form of two small satellites, flying as prototypes for Mr. Musk’s Starlink low-cost, high-performance network of internet communications satellites. Designated Microsat-1A and 1B, the prototypes reportedly weigh about 880 pounds (400 kg) apiece. Under the announced plans, the eventual network in low-Earth orbit seeks to support the bandwidth to carry up to 50 percent of all backhaul communications traffic and up to 10 percent of local internet traffic in high-density cities. In the minutes after today’s launch, the two satellites were successfully deployed and received their new names. “Tintin A and B will attempt to beam “hello world” in about 22 hours when they pass near Los Angeles,” Mr. Musk tweeted.

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