How Launch Window works

Where the data comes from

Every launch on this site comes from Launch Library 2, the public launch database maintained by The Space Devs. Launch times, statuses, pads, rockets, providers and mission details all originate there. Launch Window adds no independent observations of its own — it makes no phone calls, watches no scanners, and never publishes a launch the feed has not published.

One upstream request serves the whole site. The schedule on the home page, every /launch/ detail page and the sitemap all read the same cached copy of the same feed, so the site draws on the source lightly rather than fetching it separately for each page.

That means a fact on this site is wrong in one of two ways: it is wrong upstream, or we have presented it badly. Both are fixable — see corrections.

How often it updates

Launch data is cached at the edge in three layers:

• A live copy, refreshed on a ten-minute cycle. This is what you normally see. Between refreshes the countdown itself keeps running in your browser, second by second, from the time already loaded.
• A last-known-good copy, kept for up to seven days. If the source is unreachable or returns an error, the site serves this instead of emptying the schedule. During an upstream outage you may therefore be looking at last-known-good data rather than the current picture.
• A short negative-cache window of sixty seconds. If the source is down and there is no last-known-good copy to fall back on either, the site remembers the empty result briefly rather than re-asking on every page view.

Your browser keeps its own copy of the last schedule it loaded successfully. If the feed cannot be reached at all, the home page falls back to that copy and says so on the page — “Showing saved data from N min ago — live feed is temporarily unavailable” — rather than presenting old times as current ones.

Time precision — why we sometimes refuse to show a countdown

Not every launch time means the same thing. The feed tags each one with a precision, and Launch Window runs a to-the-second countdown only when that time is confirmed to the second, to the minute, or to the hour. Anything coarser — a time given only to the day, the month or the year — is not precise enough to count down, and the site will not pretend otherwise.

When the time is not precise, four things change:

• The clock is replaced with the words Targeted date. No digits, no ticking.
• The time is prefixed “No earlier than” wherever it appears — on the schedule, in the list, and on the launch's own page.
• The detail page describes the launch as flying no earlier than a month and year, rather than naming a day.
• The structured data search engines read carries the date only, never a made-up time — and the home page emits no event markup at all for an imprecise launch.

A precise time is still not a promise. It means the provider has committed to that moment; holds, slips and scrubs are ordinary parts of spaceflight and the status is what tells you which has happened. The launch glossary explains those words.

Status vocabulary

The feed publishes a short status code for each launch. Launch Window shows a plain-English label for it — this is the whole mapping, with nothing else added:

Go → “Go for launch”

The provider has confirmed the launch is go for its target time.

TBC → “To be confirmed”

A date and time are set, but the provider has not yet confirmed them.

TBD → “Time TBD”

The launch is planned, but the time is still to be determined.

Hold → “On hold”

The countdown is paused. A hold is not a cancellation — the clock can resume if there is still time in the window.

In Flight → “In flight”

The rocket has lifted off and the flight is under way.

Success → “Launched”

The launch flew and met its objective.

Failure → “Failure”

The launch flew and did not meet its objective.

Partial Failure → “Partial failure”

The launch flew but fell short of its objective in part.

If the feed ever sends a status this list does not cover, the site shows the feed's own wording for it, or “Status unknown” if there is none. It never guesses.

One rule is worth stating plainly, because it is easy to get wrong: a launch that has already flown — successfully or not — is recorded as having happened. A failure is not a cancellation, and neither is a partial failure. Only a launch that has no outcome at all, and whose target time has passed by more than an hour, is treated as postponed.

Timezones

Every time on this site is converted in your own browser to your own timezone. The zone is read from your browser's own settings at the moment the page renders, and the name of it is shown in the pill at the top of every page so you can check the conversion is the one you expect.

Nothing about your location is sent anywhere. There is no server-side geolocation, no guessing a timezone from your IP address, and your timezone is never stored. Server-rendered launch pages ship their times in UTC so they are correct with JavaScript switched off, then convert to your local time in your browser on load.

Two things are kept in your browser and never leave it: your choice of sky theme, and a copy of the last schedule loaded, used only if the feed cannot be reached. The privacy policy covers the rest.

Corrections

If something here is wrong, please say so: [email protected]. Including the page address and what you expected to see makes it much faster to fix.

Corrections fall into two kinds, and they are handled differently:

• Data errors — a wrong launch time, pad, rocket or mission name — originate upstream. The site holds no manual overrides, so we report these to The Space Devs and the fix reaches this site on the next refresh once it lands in Launch Library 2.
• Presentation errors — a misleading label, a broken link, a countdown shown when it should not be — are ours. We fix those here directly.

Affiliate links and advertising

Some gear and travel links on this site are affiliate links, to Amazon, Booking.com and Viator among others. They are marked rel="sponsored nofollow" in the markup and disclosed where they appear; if you buy through one we may earn a commission at no extra cost to you.

They have no influence on the launch data. Which launches are listed, in what order, and how each one is described are generated from the feed alone — there is no paid placement in the schedule and no way to buy a mention.

The site also carries Google AdSense advertising. What that means for cookies is set out in the privacy policy.

Who runs this

Launch Window is an independently operated utility site. It is not affiliated with, endorsed by, or speaking for any launch provider, space agency, or The Space Devs — it is a reader of their public data, nothing more.

For anything at all, including corrections, the contact address is [email protected].