Happy Birthday to…. (are you curious?)

We wish to express a warm happy birthday to….

… to “Curiosity”, NASA’s Mars rover, who was named by a sixth grader, Clara Ma.  Curiosity landed on Mars on August 5, 2012 (launched Nov 26, 2011) and is still continuing to send data in spite of it’s intended lifetime of 1 Martian year (686 Earth days).

Huge congrats to all or the contributing NASA centers, and especially, JPL, for an incredible project and more than a breathtaking deployment using a “sky crane” on the Red Planet.  From a conventional engineering point of view, I honestly thought this was insanity when I heard about it, but with madness comes brilliance.  A buddy of mine was on an executive rotation on this mission.  What astounding team work and brilliant people involved.

Note the rover’s use of UHF (~400MHz) for near relay link communications with orbiting Mars satellites (e.g. MRO, Odyssey)  and X-band (~8 GHz) links using steerable dish for weak signal comm via the Deep Space Networks.

Curiosity has three antennas:

  1. High Gain Antenna (HGA). A 25×29cm patch antenna with transmit gain of 25.5 dBi and receive gain of 20.2 dBi. Used for direct-to-Earth (DTE) communcations for telemetry and direct-from-Earth (DFE) for commanding.
  2. Low Gain Antenna (LGA). Gain of 5dBi. Used for low rate DFE commands. Not intended for use for DTE as the data rate is very low.
  3. UHF antenna. Used for communicating to/from Earth via the Mars relays: MRO and as a backup, Odyssey.

The HGA and LGA are used for X-band communications. The DTE transmit power is 15 W. The minimum requirement for downlink data rate using the HGA is 160 b/s to a 34-m antenna and 800 b/s to a 70-m antenna. The uplink data rate requirement is 1 kb/s using the HGA, allowing for commands to be sent to Curiosity. As a backup the LGA can be used (it has a much wider beamwidth and therefore doesn’t need as accurate positioning as the HGA), but because of the weaker signal a data rate of about 15 b/s is expected.

The downlink (relay to Curiosity) data rates range from 2 kb/s to 2048 kb/s. Odyssey only supports up to 256 kb/s. The uplink data rates range from 2kb/s to 256 kb/s (Odyssey: 8 and 32 kb/s only).  The big dish in the photos below is one of several portable antennas at the W5RRR shack.  We typically keep it stored in the backroom to avoid getting it wet…


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