Where's Webb?


This data-driven infographic shows the status of Webb on its journey to L2 orbit. The page constantly updates as Webb travels, deploys, and cools to operating temperature. If you have any issues with the page, hold the CTRL or CMD key and hit the F5 key which will reload the page and should clear any issues. (cntl/cmd shift R works too).


The graduated horizontal line on the display is a TIME line. The units are days. There are 30days on the timeline. Webb enters its L2 orbit at approimately 29.5days on the timeline. Note on smaller screens the labels are progressively removed. On portrait mobile screens of 300-600px wide only the units “days” is displayed.


The most recently completed deployment step for Webb is displayed along a timeline that also indicates the major deployment phases. Note that the timing, duration and/or order of deployment phases and steps may change. This page shows the default/nominal timing and order. The phases mark the start and end of major groups of deployment steps. The most recently completed deployment step is shown as a spacecraft icon on the timeline and is detailed below with a larger image and links. Deployment phases are shown on the timeline in a light blue overlay on screens large enough to display this info, otherwise hidden.


The speed and distance numbers displayed track Webb’s distance travelled from Earth to entry into its L2 orbit. The numbers are derived from precalculated flight dynamics data that models Webb’s flight up to its entry into L2 orbit. The distance shown is the approximate distance travelled as opposed to altitude.

Webb’s speed is at its peak while connected to the push of the launch vehicle. Its speed begins to slow rapidly after separation as it coasts up hill climbing the gravity ridge from Earth to its orbit around L2. Note on the timeline that Webb reaches the altitude of the moon in ~2.5 days (which is ~25% of its trip in terms of distance but only ~8% in time). See the sections below on Distance to L2 and Arrival at L2 for more information on the distance travelled to L2.


As noted above, this page displays the “distance travelled” by Webb as opposed to its altitude from Earth. Webb launched on the sun-facing side of the Earth and travels on a slightly curved path so Webb’s “distance travelled” is greater than its altitude. Webb passing the Moon’s altitude is a good example of the difference, when Webb reached the altitude (a) of the moon at a time of launch + ~2.5 days, Webb had already travelled a distance (d) greater than the moon’s altitude.


Temperature control is a vital aspect of Webb’s design, engineering and operations. Of the many temperature monitoring points on the observatory, this page displays 2 “hot side” and 2 “cold side” temperatures that are a good indication of overall temperature status and trends.

NOTE: temperature data will begin updating 1-2 days after launch. Displays will read “—” until that point.

The temperatures displayed on the hot side of the observatory are located on the spacecraft bus and sunshield structure. The temperatures displayed on the cold side of the observatory are located on the primary mirror and instrument (ISIM) module radiator. They are labelled with the following letters on the display (note: these labels will pop up if you hover your mouse over the display):

  • a) Sunshield UPS Average Temperature (hot side: Sunshield Structure)
  • b) Spacecraft Equipment Panel Average Temperature (Spacecraft Bus)
  • c) Primary Mirror Temperature (cold side)
  • d) Instrument Radiator Temperature (cold side)

There are many more temperature sensors on the observatory that our engineers monitor throughout the deployment, commissioning and operations processes. The data points shown here give a good overall indication of the temperature trends on each side of the sunshield as we move through deployment and commissioning. They illustrate the great contrast between the hot and cold sides of the spacecraft and the incredible engineering and effectiveness of the sunshield. These temperature observations are reported daily from actual spacecraft telemetry data. Temperature values will continue to be reported in the months that follow the completed deployment as the spacecraft cools to operational values.


L2 is approximately 1 million miles from Earth (932056 miles/1.5M km to be exact). But Webb never actually arrives at L2, it is travelling to enter an orbit around L2 . Webb’s L2 orbit is very large in size and it enters its orbit before it reaches the linear distance between Earth and L2. Webb’s orbit around L2 is known as a halo orbit which, rather than a single path, is an orbit that periodically varies through a series of paths around L2.


By design, the launch vehicle and Webb’s trajectory put Webb on a path to an L2 orbit with only small inputs needed to refine it. As it separates from the upper stage of the launch vehicle, Webb is climbing the gravity ridge from Earth up into a halo orbit around L2. Once Webb is in its halo orbit it will be riding up and down and over and along the shallow saddle contour at L2.

To get the exact orbit needed, Webb’s trajectory is fine tuned by a number of “burns” along the way. You can learn more about these Mid Course Correction (MCC) burns on the Deployment Explorer page. The final burn, MCC2, inserts Webb into the desired L2 halo orbit. The MCC2 burn is nominally planned for Launch + 29days. At the end of that burn we can say Webb is “In L2 Orbit” and so has “arrived at L2”.

Therefore, this page, for purposes of calculations uses a distance to L2 orbit entry number ( and timing ) that is a sufficient distance and time after the MCC2 burn to say “Webb is in L2 Orbit”. Once in L2 orbit, this page will no longer track distance, but will track temperatures. The spacecraft will continue to cool to operating temperatures and numerous tests and calibrations occur to ready it for operations and its first images over the months that follow.


By default the page loads and displays distances in miles, temperatures in Fahrenheit, ie English/US units (also known as Imperial or USCS system units). If you wish to have the page load and display in kilometers and temperatures in Celcius, ie metric system units use the urls below to select your prefered units. We do not use cookies; these urls ‘store’ your units preference. Once chosen, bookmark the urls with your prefered units and use it instead of the default website link. NOTE: the page units toggle button English<>Metric now reloads the page with these urls.

3 Points