Tuesday, September 10, 2019

India's Lunar Probe May Still Be Alive

But probably isn't.

Last Friday, India's Vikram lunar lander was on approach to landing near the moon's south pole when contact was lost with the probe near the end of its descent.  India's Space Research Organization (ISRO) reports contact was lost when the probe was 2.1 km (1.3 mi) above its lunar landing site, and they have been attempting to contact the probe since then.  That aside, the mission has been successful: India has successfully placed a world-class, high-performance spacecraft - the Chandrayaan-2 orbiter - into a safe lunar orbit.  The orbiter is unaffected by this and will likely be returning high quality data to Earth for a long life.  It's expected to live seven years.

So far, only the US, Russian, and Chinese space agencies have landed satellites on the moon.
ISRO lost communication with Vikram just 2.1 km above the surface of the Moon. The lander was traveling a bit less than 80 m/s (180 mph), a speed that can be contextualized as ~95% of the way to landing relative to the lunar orbital velocity it started at.
  • A minute or so before communication was lost, an ISRO graphic showing the spacecraft's altitude, velocity, and orientation appeared to indicate some major issues with attitude control. The lander appeared to be spinning out of control, perhaps the result of a failure of one of its several landing engines, its attitude thrusters, or avionics mechanisms needed for the craft to orient itself.
  • The loss of communication makes it extremely hard to conclude anything with certainty at this stage of the investigation process. The fact that the lander appears to be intact suggests that it could have continued fighting to lower its relative velocity in the final 2.1 km, 

Vikram lander with the Pragyan rover visible on a ramp.  ISRO photo from Ars Technica.
Fascinatingly, rumor has it that the Vikram lander - despite lack of communication and a thoroughly anomalous landing attempt - is actually intact on the surface of the Moon, instilling hope that the lander may still be partially salvageable. According to those unofficial reports, Vikram somehow came to land on the lunar surface with no (or very few) parts visibly missing.
  • ISRO reportedly was able to rapidly capture detailed photos of the landing site with its new Chandrayaan-2 orbiter, visually confirming the intact nature of the lander. However, it also showed that Vikram came to a rest on its side or fully upside-down, dramatically increasing the odds that communication will never be restored.
It's a foregone conclusion that if the lander is upside down or even on its side, the planned deployment of its small lunar rover isn't going to happen.  The rover, named Pragyan, ("Wisdom" in Sanskrit) is small and was not expected to survive the lunar night due to not having enough battery capacity to run heaters over the potentially two week long night.  The 27-kg (60 pound), six-wheeled rover was expected to roam up to 500 meters across the Moon.  

ISRO has been trying to contact and hear back from the lander since Friday using the big dishes of NASA's Deep Space Network, never receiving anything from the probe.  This argues that it's very likely to be dead.

All of the indented quotes are from today's Teslarati email newsletter DeepSpace.  I've tried to find something on the Teslarati website that I can link to, but the newsletter doesn't show up. 


  1. I read they lost the lander the other day, but that was all. I hadn't heard the telemetry showed something obviously wrong until your post. Hopefully they'll find the problem when they analyze the telemetry further.

    I know how they feel. It's a Really Bad Day when the project you've put years into is catastrophically lost.

    1. I worked on a satellite for the JPL that was one of the first to use a radar scatterometer to measure wind speed on the open ocean. There was really only one system on board that couldn't be redundant, the slotted waveguide antenna.

      Guess what failed in orbit?

    2. Awwwww.....RATS!

      HITH can a piece of pipe fail?

      Well, rectangular tubing with slots cut in it, but still, a "piece of pipe".

      Feedpoint failure?

      Was it S-Band, C-band, or "other"?

    3. Speculation was that it hit orbital debris. IIRC, signal strength went down, the system seemed to be tumbling, and it died pretty quickly. It was in orbit, doing its job and something happened that caused it to die within a minute or so. Again, IIRC - this would have been about '95 or so.

    4. Oops. Forgot. It was on 14.0 GHz.

    5. Ahh...the 'bottom end' of Ku band. Been there many times.....

      "Orbital Debris" is a genuine "Murphy Moment".....

  2. Murphy is a bitch. Single failure items will.

    1. One thing we can be sure of in a world of uncertainty.

  3. As Israel and now India have learned, the hard way, successfully landing on the moon is no easy feat, even 50 years after the USA sent and safely brought back two men from our nearest space neighbor. Not to mention that the USA accomplished that feat with machines designed using slide rules, using flight computers that didn't have anywhere near the computing power of most of today's smart phones.


    1. Before I decided on the matter-of-fact title, this post was going to be called, "Rocket Science is Hard - M'Kay?"

      It really is a tribute to those guys in the '60s who figured out how to land on the moon when there was serious debate about it even being physically possible to land on the moon. There were plenty of scientists who thought any lander would sink into deep dust and be lost.