It doesn’t occur too often that Arizona skies may be staging the brief spectacle of a rocket slicing into the upper atmosphere but they may this weekend. SpaceX’s Falcon 9, the 230-foot two-stage rocket ship, will blast off from Vandenberg Space Force Base in California on Sunday, Sept. 28, to place 24 Starlink satellites into low-Earth orbit. The four-hour launch window opens at 4:32 p.m. Pacific Time, but the afternoon schedule will make daylight rival visibility for viewers some hundreds of miles east of the pad. The south or southeast direction and sun-synchronous optimized orbits will be the Falcon 9’s launch trajectory out of Launch Complex 4E.
Although the rocket is typically visible over much of California and into Arizona during night or dusk flights, daylight and distance will make this view more elusive. Visibility is based on numerous variables altitude under power, atmospheric state, and light. Twilight launches can be magnificent, with sunlight-bathed exhaust clouds high in the upper atmosphere above a darkening landscape, but in direct sunlight, rocket vapor trail versus sky contrast rapidly fades. Arizona observers who are resolved to give it a go are served best by location.
High positions with clear horizons and low light pollution have the best prospect. Among the top-ranked choices: Dobbins Lookout on South Mountain in Phoenix, ridges at Papago Park, and Fountain Hills, a Dark Sky Community since 2018. The Superstition Mountains east of Phoenix, Cave Creek north of Fountain Hills, and Black Canyon City in Yavapai County also offer unobstructed sightlines. Even city locations such as Phoenix Sky Harbor International Airport parking garage can be used as vantage points, though background light will diminish contrast. A little farther away are Estrella Mountain Regional Park, Skyline Regional Park, White Tank Mountains, San Tan Mountain Regional Park, Monument Hill, and Casa Grande with their unobstructed skies. The mission is just one part of SpaceX’s regular deployment of the Starlink satellite constellation, which now includes over 7,000 active spacecraft.
Flying at altitudes of about 341 miles, Starlink’s constellation of low-Earth orbit provides broadband internet with less lag than traditional geostationary systems. The architecture supports high-bandwidth applications like streaming, online gaming, and video conferencing, and is strategically valuable for commercial and military communications. The service is added gradually by each mission, and SpaceX reported that 24 missions would provide global service saturation. The Falcon 9’s first stage is propelled by nine Merlin engines firing RP-1 kerosene and liquid oxygen for 1.7 million pounds of thrust.
The second stage, utilizing a single vacuum-optimized Merlin engine, serves for orbital insertion. The booster for this mission is expected to be flight-proven, carrying on the reusability tradition of SpaceX boosters have flown as many as 16 times and landed successfully on autonomous drone vessels such as *Of Course I Still Love You*. The strategy has reduced the cost of launch by orders of magnitude, allowing for high-frequency flight such as the recent three Falcon 9 launches in under 41 hours. By eye’s capability to see, liquid-fueled rockets such as Falcon 9 generate less flamboyant fires than solid-fueled spacecraft, and their contrails persist less.
In darkness, the radiant engine plume and diffusing contrail may be seen for hundreds of miles, but in daylight, haze and atmospheric scattering will abbreviate the spectacle. Phoenix viewers should gaze in the direction of an azimuth of around 282°, and Tucson viewers around 290°, as the rocket emerges over the horizon. Although the rocket may be difficult to spot with the naked eye, the mission will be felt in space.
Starlink development is transforming the satellite communications industry, merging with ground-based 5G networks and extending connectivity to distant or infrastructure-scarce areas. For hobby astronomers, the launches also bring opportunities and challenges as the expanding constellation impacts views of the evening sky. Whether observed blazing through the Arizona skies or followed via a livestream, Sunday’s launch of a Falcon 9 is another march in the breakneck pace of contemporary space operations.
