Guiding the James Webb Space Telescope to Orbit
By Danny Baird
July 12, 2022
Just six months after launch on Christmas 2021, NASA's James Webb Space Telescope has transmitted its first science images. These images demonstrate the capabilities of Webb, a high-resolution infrared observatory recognized by many as the most powerful telescope ever launched to space. Webb-enabled astronomy could reveal new secrets of the early universe and aid in the study of worlds beyond our own.
The Flight Dynamics Facility (FDF) at NASA's Goddard Space Flight Center in Greenbelt, Maryland, has played a critical role in Webb's journey to this important milestone. As the physical location for all Webb Flight Dynamics Team (FDT) operations, the facility provided necessary infrastructure and staff to design and track the telescope's trajectory.
From the FDF, the FDT supported mission launch through spacecraft separation, providing acquisition data to the Near Space Network's constellation of Tracking and Data Relay Satellites (TDRS). This data empowered the TDRS constellation to track the observatory between about three and 28 minutes after launch.
After Webb separated from the Ariane 5 launch vehicle, the FDT determined the observatory's orbit using European Space Agency ESTRACK Malindi and NASA’s Deep Space Network tracking data measurements during the first seven hours of the mission. This helped facilitate the first trajectory correction maneuver, which took place about 12.5 hours after launch.
Along with this first mid-course correction, FDT planned, monitored in realtime, and calibrated the two subsequent corrections designed to set the telescope on course for its final destination near the Sun-Earth/Moon L2 libration point. The team monitored these events in real-time at the FDF, relying on tracking data measurements from the Deep Space Network.
These FDT-designed maneuvers required absolute precision, as Webb could not reverse course if it overshot its targeted orbit. Doing so would have damaged the telescope's sensitive mirrors and instruments due to light and heat from the Sun. The FDF also had limited time to plan these trajectory corrections, basing their first mid-course correction with only seven hours of Deep Space Network and ESTRACK range data.
James Webb’s final orbit is about a million miles from Earth at the second Sun-Earth/Moon Lagrange point, or L2. Positioning the telescope in a controlled heliocentric orbit keeps it in line with Earth as it orbits the Sun and allows the sunshield to protect delicate instruments from harsh solar radiation.
Thanks in part to the dedication and responsiveness of the FDT team, Webb arrived at its final destination. The exceptional performance of the mission's Ariane 5 launch vehicle meant that the telescope reached L2 with surplus fuel. This extra propellant could extend the telescope’s operational life well beyond NASA's 10-year science lifetime. (The minimum baseline for the mission is five years.)
As the James Webb Space Telescope enters science operations, the FDT team will continue to empower the mission with vital navigation services, determining Webb's orbit, predicting its trajectory for science planning, and planning station-keeping maneuvers to maintain the L2 orbit as the observatory gleans new insights into the universe's origins. FDT support at the FDF for Webb will continue until the end of the mission.