Say, you are the leader of a nefarious country that is in posession of submarines equiped with long range nuclear missiles. You want to launch a stealth missile attack codenamed "Operation Orange Squeeze" on a northern hemisphere Super Power.
Where would you direct your submarine, and where would you best fire you missiles, from the perspective of an as-late-as-possible space-based detection of your missile launches?
The answer came to me today when, after a question by someone (in the context of a war crime investigation), I looked into the current global coverage of the Space Based Infra Red System (SBIRS), the US system of Early Warning satellites that looks for missile launches:
 |
| click map to enlarge |
The red areas in the map above have an almost continuous coverage by SBIRS satellites (and often by multiple SBIRS satellites at the same time). The dark blue and black areas in the map by contrast have only a few minutes of SBIRS coverage each day, or even none at all.
As you can see, there is a clear gap in coverage in the southeastern Pacific, with lowest coverage in the area near the Galapagos islands. That is where I would park my nuclear missile submarine.
You might have to be quick to pull off your nefarious plan though. A new SBIRS satellite, the fourth satellite in the geostationary component, will launch in January. It wouldn't surprise me if it stops the gap, once operational.
Of course, this map is in fact somewhat deceptive anyway. It only shows the coverage by SBIRS. But there is also the legacy early warning satellite system called DSP (Defense Support System), which still has active satellites, and which is not taken into account here [UPDATE: but see the plot at the end of this post!]. It is less sensitive than SBIRS, but likely will detect your
Back to SBIRS. SBIRS is made up of two components, each currently consisting of three satellites (so six in total): three geosynchronous SBIRS-GEO satellites at geostationary altitude, and three SBIRS-HEO satellites (TRUMPET-FO SIGINT satellites with a piggy-back SBIRS package) in 64-degree inclined Highly Elliptical Orbits with two revolutions a day.
 |
| click map to enlarge |
The map above shows the coverage of the three geosynchronous SBIRS satellites (a fourth will be launched in January). Eurasia, Africa and the western Pacific Ocean has a continuous coverage by these satellites, with central Asia, Pakistan and India (the latter two known nuclear powers) particularly well covered.
The SBIRS-HEO coverage is more variable and depends on the date and time of day, but the system is designed such that at least one of the HEO satellites will have much of the Northern hemisphere in view at any time. Here are a few examples, for various times of the day: note how coverage of the Northern hemisphere is near-continuous (the HEO component also particularly covers the Arctic region well, which is at the edge of the GEO component's coverage).
 |
| click maps to enlarge |
In the case of a missile launch, the sensors pick up the heat signal of the missile engine. Because of the large degree of worldwide coverage which the system now provides, an undetected stealth launch of a nuclear missile has become almost impossible.
SBIRS is probably an important source of Early Warning capacity and information on the recent North Korean missile tests.
UPDATE 20 Dec 2017 23:25 UT:
I now also included the four DSP satellites that are still operational according to the database of the Union of Concerned Scientists. That leads to the following map:
 |
| click map to enlarge |
