Saturday 13 June 2020

A French M51 SLBM test with a 6000 km range on June 12

click image to enlarge

On the morning of June 12, 2020, the French Navy test launched an unarmed M51 SLBM from the Triomphant-class submarine Le Téméraire.

The launch was from a spot near the French coast just south of Audierne Bay in Bretagne, not far from the French Naval port of Brest, according to a French Government bulletin. Navigational Warnings place it around 47o.65 N, 4o.15 W. The launch direction was towards the Caribean, with impact in the Atlantic Ocean near 24o.4 N, 66o.1 W according to the same Navigational Warnings.

The locations of the hazard areas from these Navigational Warnings point to a 6000 km flight trajectory (see figures above and below):


DNC 08.
A. 47-12N 010-25W, 47-49N 004-31W,
47-39N 004-01W, 47-24N 004-11W,
46-44N 010-17W.
B. 46-17N 019-54W, 46-50N 017-09W,
45-07N 016-29W, 44-35N 019-01W.
2. CANCEL THIS MSG 111200Z JUL 20.//

Authority: NAVAREA II 167/20 042002Z JUN 20.

Date: 060713Z JUN 20
Cancel: 11120000 Jul 20



39-37N 040-14W, 40-40N 037-48W,
39-41N 037-07W, 38-39N 039-31W.
B. IN AREA WITHIN 92 MILES OF 24-24N 066-06W.
2. CANCEL THIS MSG 111200Z JUL 20.//

Authority: AVURNAV BREST 070808Z JUN 20.

Date: 070851Z JUN 20
Cancel: 11120000 Jul 20

I have plotted the Navigational Warnings on the map below. The line shown is a simple STK-modelled ballistic trajectory, which fits these area's well. Assuming a 1200 km apogee, the flight-time should have been around 23 minutes.

Click map to enlarge

The M51 is  the newest French SLBM. It is in service since mid-2010. It has three stages and can carry up to 10 RV's. It's maximum range is said to be near 11 000 km, i.e. comparable to the Trident-II SLBM of the US Navy and Royal British Navy. This is the 5th succesful test of an M51 SLBM (a 6th test attempt in May 2013 ended in failure).

A nice summary of what is known from public sources about this test is provided in this article by Tyler Rogoway on The Drive.

Note added
For those interested in these issues: last year, I did an in-depth analysis of several Trident-II SLBM test launches, including one that was serendipitously photographed by an astrophotographer from the Canary Island. The latter observation allowed to estimate the apogee altitude of that test.

Thursday 11 June 2020

SkyTrack: a simple tool to calculate satellite positions and visuallize satellite trajectories in Google Earth

Over the past years I have written a number of simple software tools to ease some of my data analysis. Some of these I have released into the wild through my software webpage. Others, which are more experimental, I keep to myself for now.

This week I have released another tool into the wild: SkyTrack.

SkyTrack (now in version 2.5) was initially written by me to quickly create a datafile with geographic coordinates of the trajectory of a satellite, in a format that is easy to import in QGIS, the mapping application that I use to make the trajectory maps that you frequently see in my blog posts.

It has since evolved and is starting to get to a point where it might be useful to others, hence why I release it now.

The output of the program is numerical (a table with data), not graphical, which will limit the usefulness to many people. However, as of the latest version (2.5) the program has the option to generate a .kml file of the trajectory for import in Google Earth (if Google Earth is installed on your pc, it will actually auto-open it and load the .kml, after saving).

When the .kml is loaded into Google Earth, the resulting images look like this:

The program takes lines 1 and 2 of a TLE as input (you copy/paste them into the input textbox). You then provide it with a time window, a desired time step, and an observing site.

It will then calculate the ground-track (the subsatellite-point) over that time window, in the given time steps; it will also calculate the altitude above the Earth at each time instance; the range to the observing site and the satellite's position in both RA/DEC and azimuth/elevation as seen from the observing site. It will also provide an indication whether the satellite is sun-illuminated at each time instance

As optional output, the program can add EFG (ECEF) X, Y, Z coordinates, as well as the EFG velocity vector. It can also calculate the Doppler-shift corrected radio frequency for the satellite, if a center frequency is given.

There are also options to restrict the program to only provide output when the satellite is a specified distance in degrees above the horizon as seen from the observing site, and/or only provide output when the satellite is sun-illuminated.

There are a number of options as well regarding the output format. A pdf with the download provides instructions for use.

The program is currently only available for 64-bits Windows. It employs Microsoft's .NET framework, and SGP4 DLL's that are courtesy of the US AFSPC.

For the future, I want to add some direct graphical output options, but it might take a while before I get to that. So far, development of this tool was largely done when the need for a specific feature arose.

Wednesday 3 June 2020

Introducing a new web resource: Launchtower

Before new launches, I frequently publish orbital element (TLE) estimates that can help satellite observers plan observations of the payload and/or associated rocket stage directly after launch.

Untill now, I published these pre-launch estimated TLE's on the SeeSat-L Mailing List and occasionally also on this blog. And I will keep doing that: but I realized that it would perhaps be good to have a central website for these pre-flight TLE's.

So I introduce to you: Launchtower (

The TLE estimates in question are based on public information about the launch site, launch date and launch time, and (if made public) the orbital altitude and orbital inclination aimed for.

For classified launches (where this information usually is not available), educated guesses are made based on amongst others information gleaned from NOTAM's and Navigational Warnings. These provide information on launch time windows, and the orbital inclination aimed for, which can often be deduced from the launch azimuth, which in turn can be deduced from the locations of the launch hazard areas and upper stage deorbit areas found in Navigational Warnings.

The website will provide TLE estimates for launches that are "of interest". The criteria for what comprises "of interest" are basically:  those launches that are of interest to me.

Generally speaking, these will be: classified launches; human spaceflight; and launches that overfly Europe on the initial revolution.

TLE's can be used to plot a sky track for your location, using predictive software like for example HeavenSat.


On request, I have added a plain-text file URL as well, to which you can point software that can (stupidly) only load TLE's from plain text files on a web-adres. Link is on the main Launchtower page.