Billions of {dollars} of observatory spacecraft orbit round Earth or in the identical orbit as our planet. When one thing wears out or goes incorrect, it will be good to have the ability to repair these missions “in situ”. To date, solely the Hubble House Telescope (HST) has loved common visits for servicing. What if we may work on different telescopes “on orbit”? Such “fixit” missions to different services are the topic of a brand new NASA paper investigating optimum orbits and trajectories for making service calls on telescopes far past Earth.
Among the most efficient orbiting telescopes function on the Solar-Earth Lagrange factors L1 and L2. Presently, these positions afford us some very unbelievable science. What they will’t afford is simple entry for repairs and servicing. That limits the anticipated lifetime of services reminiscent of JWST to about 10-15 years. Sooner or later, extra missions might be deployed a Lagrange factors. These embody the Nancy Grace Roman Telescope, ESA’s PLATO and ARIEL missions, and the Giant Ultraviolet Optical Infrared Surveyor (LUVOIR).
These observatories want propellants for perspective thrusters to assist them keep ‘in place’ throughout their observations. There’s solely a lot “fuel” you possibly can ship together with these observatories. As well as, parts put on out, as they did with HST. So, individuals are methods to increase their lifetimes by means of servicing missions. If failing parts could be changed and propellant delivered, the lifetimes of those observatories must be prolonged fairly a bit, giving astronomers extra bang for the observational buck.
Planning Future Spacecraft Servicing Missions
Researchers on the Satellite tv for pc Servicing Functionality Workplace (SSCO) on the Goddard House Flight Middle (GSFC) investigated the probabilities for servicing missions to distant area telescopes. In a not too long ago launched paper, they concentrate on the feasibility of on-orbit refueling missions for area telescopes orbiting at Solar-Earth Lagrange 2 (SEL2).
There are a lot of challenges. For one factor, present-day launch applied sciences are (at this writing) insufficient to do this form of mission at such distances. Clearly, the know-how has to advance for servicing visits to happen. As well as, it’s vital to keep in mind that present telescopes, reminiscent of Gaia and JWST, weren’t designed for such entry. Nonetheless, future telescopes could be fitted with servicing ports, and so on. to allow servicing. Lastly, there are the challenges of really getting the servicing missions to the observatories.
The Goddard workforce targeted on this remaining difficulty by computing fashions of varied launch and orbital options for such missions. Not solely did they have in mind the launch trajectories themselves, but additionally Solar-Earth-Lagrange level dynamics, plus the relative positions of observatories at SEL2. As well as, the workforce thought of the steadiness of the observatories throughout and after rendezvous and attachment. All of those components rely when planning whether or not or not a servicing car could be launched at an affordable price to increase the lifetime of the observatory sufficient to take the time definitely worth the time and expense.
Getting a Spacecraft Refuelling Mission Underway
The workforce created fashions for a theoretical mission for on-orbit fuelling at SEL2. That’s the place JWST and Gaia are sitting, for instance, together with WMAP, Planck, and others. The paper examines robotic refueling missions out to SEL2 for modeling functions.
To try this, nevertheless, there have to be an optimum trajectory for the robotic spacecraft to take out to SEL2. They want to have the ability to carry out autonomous navigation to the proper level in area. As soon as on the goal observatory, the refueling robotic would then have to make a cautious strategy for its docking maneuvers. That requires on-orbit evaluation of the goal’s movement in area with respect to the Solar in addition to its place in its SEL2 orbit. Docking itself can have an effect on the observatory’s place and movement and the robotic must take that under consideration, as nicely. The concept is to maintain the observatory in the identical place after docking.
Nonetheless, the large query is: how will we get it on the market inexpensively, quick, and protected?
The Goddard workforce primarily investigated the perfect and best trajectories to get to SEL2. Particularly, they checked out the perfect approaches to get to the Gaia spacecraft, which is able to run out of its propellant someday within the subsequent yr. In addition they examined JWST as a potential goal for such a mission. If such a mission was potential in the present day, these observatories would achieve years of “level and shoot” entry to the Universe.
How you can Get There
Of their paper, the workforce appears to be like at two approaches to the SEL2 refueling mission. One is a direct launch trajectory from Earth and the opposite is a spacecraft leaving from a geostationary switch orbit (GTO). They assumed that the purpose of the mission was the quickest potential restoration of telescope operation. That dictates the shortest and most secure potential trajectory alongside which the spacecraft can keep fixed thrust.
The Goddard workforce created a “ahead design” strategy for computing low-energy and low-thrust transfers from an Earth departure orbit to an area telescope orbiting the SEL2 level. Then they did the identical for a servicing spacecraft leaving from a degree in geostationary area. Basically, both an Earth-departure or GTO-centric departure will work. As soon as the robotic servicing mission leaves Earth orbit, it travels at low thrust throughout a spiraling transit to SEL2. As soon as there, it does a rendezvous with the goal, matches its movement in area, after which “locks on” to carry out its supply mission.
It’s vital to keep in mind that a launch from Earth or GTO is a part of a number of options to SEL2 servicing missions. The workforce’s evaluation resulted in a simplified technique of producing potential orbits and trajectories for such actions. You’ll be able to learn the complete textual content of their detailed evaluation of the totally different trajectory options on the hyperlink under.
For Extra Data
Mission Design for House Telescope Servicing at Solar-Earth L2
JWST Residence Web page
Gaia Telescope