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Shijian-31: a satellite with an orbit we have never seen before
China launched Shijian-31 on June 16 from Xichang, officially described as a "space environment detection" mission. The orbital elements suggest more going on.
The inclination 63.46° sits at the value where perigee advance goes to zero. Anyone who's tracked Molniya-class satellites will recognize that immediately.
But the resemblance stops there. A classic Molniya parks its apogee over high northern latitudes and dwells for hours, that's the whole design premise. SJ-31's argument of perigee is 171°, which puts perigee near the equator and its apogee on the opposite side. (Image 1: SJ-31 at 171° argument of perigee vs. a generic Molniya at 270° argument of perigee.)
So the long dwell isn't over any particular latitude — it's over altitude. Apogee reaches ~39,900 km, about 4,100 km above the operational GEO belt where comms and missile-warning satellites sit. Nearly a third of each 12.5-hour orbit is spent above that shell, crossing it twice per pass at a steep 63° angle. (Video 1: SJ-31's orbit visualized with example GEO assets.)
It's also not fixed on one region. The period is just off a clean repeating ground track, so the sub-apogee point slowly drifts around the globe — sweeping past every longitude roughly once every 24 days.
Net effect: an orbit that periodically looks down on the entire GEO belt from above, at an angle, on a rotating schedule, rather than fixating on one target.
What's it actually doing up there?
@SpaceNews_Inc @BreakingDefense @joroulette @shell_jim @planet4589 @IntegrityISR
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Pakistan's PRSC-EO3: an unusual orbit for an optical satellite
Radar tracking via @LeoLabs. Processed via COMSPOC SSA.
PRSC-EO3 (visualized in cyan) launched April 25, 2026 on a Long March 6. It's an optical imager — but its orbit is curious.
Most optical LEO satellites use sun-synchronous orbits (~97-105° inclination), which provide consistent lighting for imaging. PRSC-EO3 is in a 38° inclined orbit instead. This sacrifices global coverage and consistent lighting, but increases revisit rates over a specific latitude band: 20-40°N. That's India, Kashmir, and Pakistan.
Now consider PRSC-S1 (visualized in pink), Pakistan's SAR satellite launched July 2025, sitting in a 41° orbit. Similar inclination, similar altitude — but their RAANs are ~175° out of phase. When one passes over South Asia in daylight, the other passes in darkness.
SAR works day and night. Optical needs sunlight. The geometry appears to allow complementary coverage.
We ran the access analysis [Image 1]. The SAR sensor (unconstrained) and optical sensor (daytime-constrained) together provide repeatable revisit across day and night. The gaps left by one are filled by the other.
Then there's PRSC-HS1 — a hyperspectral satellite in SSO [Image 2], capable of detecting camouflage and identifying materials from orbit.
Optical shows you the picture. SAR shows you the picture at night and through weather. Hyperspectral tells you what you're looking at.
Five remote sensing satellites in 16 months [Image 2]. All launched by China. All with orbits favoring South Asian coverage. The stated missions are civilian. The orbital architecture appears consistent with a multi-modal ISR constellation.
@shell_jim , @planet4589, @joroulette, @SpaceNews_Inc , @IntegrityISR
#Pakistan #Space #SAR #ISR #PRSC
When HEO acquired Continuum-1, we committed to using it to catalogue objects in low-Earth orbit (LEO). Part of that work means turning attention to derelict hardware.
As noted in the recent issue of the @IntegrityISR Flash, CZ-6A upper stages are a growing concern to the sustainability of LEO as they have produced some of the largest fragmentation clouds in LEO in recent years. These rocket bodies are left in orbits that will take years to decay, with no means of manoeuvre and no plan for removal.
This is one of them.
Continuum-1 imaged this CZ-6A rocket body in orbit. It is the upper stage from the October 31, 2023 launch that carried the Tianhui 5A and 5B satellites. It appears largely intact and is gravity-gradient stabilised.
Images like these establish a baseline. If the object's state changes, that deviation is observable and comparable against something real. Attribution is rarely straightforward after a fragmentation event. A prior record can make the difference between knowing something happened and knowing why.
Reference: isruniversity.com/2026/05/19…
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A first for me. Published an article, "Developing and testing China’s Guowang constellation" in The Space Review. thespacereview.com/article/5…
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From the battlefield to the digital frontlines, @IntegrityISR is scaling mission-critical training with ISR University and #CanvasLMS, making learning flexible and impactful for defense forces worldwide. 🚀
👉 Dive into their story here: bit.ly/42FplEV
#EdTech #ProfessionalDevelopment #Training
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We're here to help inspire and motivate innovators, which is why we took part in a @usairforce #STEM event for the premier of @CaptainMarvel at @airandspace. Watch more here: bit.ly/2TLk6Tz











