Talking with Webb using the Deep Space Network

NASA’s James Webb House Telescope is almost 1 million miles (1.5 million kilometer) away from Earth, orbiting across the sun-Earth Lagrange level 2. How can we ship instructions and obtain telemetry—the science and engineering knowledge from the observatory—from that distant? We use the DSN (Deep Space Network) to speak with the observatory. We obtain knowledge when we’ve got a contact with Webb utilizing a DSN antenna

Sandy Kwan, the mission interface supervisor for Webb inside the DSN, notes that “every mesmerizing Webb picture that has graced our screens wouldn’t have been potential with out the help of the DSN antennas and personnel, the spine of interplanetary communication.”

The DSN has three websites around the globe, every positioned 120 levels aside. There are antennas in Goldstone, California; Canberra, Australia; and Madrid, Spain. This enables us to speak with Webb at any time of day, because the Earth rotates. The DSN is managed by NASA’s Jet Propulsion Laboratory (JPL) in Southern California. Kari Bosley, the lead Webb mission planner on the House Telescope Science Institute (STScI), walks us by extra of this communication course of between Webb and the DSN.

“How can we plan contact time with Webb? It isn’t so simple as choosing up the cellphone and calling the telescope. To ensure that Earth to attach with Webb there are some things that occur previous to scheduling a contact. On common, the Webb mission operations center connects with the observatory a minimum of two to 3 instances in a 24-hour interval. There are mission planners at STScI the place the Mission Operations Middle (MOC) is positioned, mission schedulers at JPL, and naturally on the DSN complexes. The mission planners at STScI work along with the mission schedulers at JPL to create contacts with Webb.

“How do we all know after we can contact Webb? The Flight Dynamics Facility at NASA’s Goddard House Flight Middle sends the MOC at STScI the view intervals wherein the observatory is seen from these three completely different DSN websites. The mission scheduler compares these instances to what’s out there within the scheduling system the place different missions are competing for time with their spacecraft.

“All missions require particular quantities of time to speak with their spacecraft, and the timing will depend on the place the spacecraft are in space. There are occasions when conflicts between a number of missions request the identical useful resource on the identical time. When this occurs, our mission scheduler at JPL will negotiate with different missions to come back to a compromise that satisfies the entire missions. As soon as all negotiations are full, schedules are despatched to the mission planners as much as six months upfront. The scheduling for the primary eight weeks is mounted, with no modifications allowed except there’s an emergency or necessary occasion with a spacecraft. The later intervals are topic to persevering with negotiations.

“Every of the DSN complexes has various kinds of antennas, together with 70-meter (230-foot in diameter), 34-meter (111-foot in diameter), and 26-meter (85-foot in diameter) antennas.

“The DSN complexes use the 34-meter antennas to speak with Webb with the 70-meter antennas as a backup. The DSN helps completely different radio frequency allocations, such because the S-band and Ka-band frequencies that Webb makes use of. S-band has a decrease bandwidth, and we use that to ship instructions to the spacecraft (e.g., begin recorder playback), to obtain engineering telemetry to watch the well being and security of the observatory, and for ranging. Ranging is the method of figuring out Webb’s place and trajectory by the delay between when the sign is distributed up and when it’s acquired again on the bottom.

“We use Ka-band to downlink saved science and engineering knowledge, and a few telemetry from the spacecraft. If we used S-band to downlink knowledge, it might take many days to obtain every day’s knowledge. With Ka-band, it takes a lot much less time, and we are able to normally full obtain the entire saved knowledge in a few hours. The high gain antenna on Webb is used for Ka-band downlink and the medium achieve antenna is used for S-band uplink and downlink when each antennas are pointed straight on the complicated for a contact. Most of our contacts are two to 6 hours in size. Usually, we request a minimum of four-hour contacts. Since DSN hosts virtually 40 completely different missions, scheduling is sophisticated.

“There are occasions when our contacts are very brief and instances when they’re longer. In every contact, you will need to downlink as a lot knowledge as we are able to because the telescope regularly makes science observations and acquires extra knowledge. When we’re not involved, the telescope continues to autonomously carry out science observations. These knowledge are saved on a solid-state recorder and downlinked on our subsequent contact. After the Webb MOC at STScI receives the information and ingests them into the Barbara A. Mikulski Archive for Space Telescope for processing and calibration, the observers will obtain the information from their observations.

“These inquisitive about seeing the downlink and uplink between NASA missions and the DSN can go to the ‘Deep House Community Now’ web site at https://eyes.nasa.gov/dsn/dsn.html. You may view the missions and assets which are actively getting used at DSN.”