Just to let everyone know, cards are going in the post today to the MER Engineering team at JPL and the MER Science team at Cornell...printed inside is the message

"To a special little person,
On a very special day,
Have a very Happy Birthday,
You're one year old today!"

And I've written
in the one to the Engineering team..

To Jake, Byron, Bill and the MER Engineering Team,
HAPPY SOL 668

Many thanks for your hard work, dedication and the director updates, your efforts in keeping them roving are hugely appreciated

With best wishes

Doug Ellison and everyone at Unmannedspaceflight.com
(PS - Flight Director gets the badge!)


and in the one to the Science team

To Steve, Jim and the MER Science Team,
HAPPY SOL 668

Many thanks for your hard work and outreach efforts in sharing the greatest field trip the solar system has ever seen

With best wishes
Doug Ellison and everyone at Unmannedspaceflight.com
(PS - SOWG Chair gets the badge!)
(PPS - Sorry - no Cake - it's an ITAR thing)

And on the back of each envelope

NOT TO BE OPENED UNTIL SOL 668A!!

I checked with SS and I managed to find appropriate addresses which should get thru to the right people.

Given the state of the postal service here, I thought it best to get them sent off sooner rather than later. JUST after I sealed the envelopes, I thought of writing (PPS - Sorry -No Cake - it's Pathfinder heritage and needs a total redesign) in the engineering one


Doug

Doug:

I hope you posted it using Mars postage stamps...

Bob Shaw

Isn't there 669 SOLs in a martian year??

Nope - I googled a lot on this one, it's 668.something sols in a martian year.

http://www.absoluteastronomy.com/encyclope...ing_on_mars.htm

"On Mars, the northward equinox year is 668.5907 sols, the northern solstice year is 668.5880 sols, the southward equinox year is 668.5940 sols, and the southern solstice year is 668.5958 sols. Averaging out over an entire orbital period gives a Martian tropical year of 668.5921 sols."

Doug

668.5921 Sols in the Martian Tropical year.

However Sol 1 started on Midnight of the day before landing so the anniversary of that would be on Sol 669.5921. Landing was at 14:34 on Sol 1 so 1 full year on mars would be on Sol 670.199 or Nov 21, 3:54:40 UTC.

I think.

Shouldnt have bothered.

Must remember to celebrate my birthday a day late this year then



Doug

You are right.
Sidereal Rotation Period (Length of Day)

1.026 Earth days 24.62 hours
By Comparison: Earth's rotation period is 23.934 hours.

Sidereal Orbit Period (Length of Year)

1.8807 Earth years
686.93 Earth days

Mars soles = 686.93 Earth days * (1 Mars days/1.026 Earth days) = 669.522 Mars days

Closer to 670 Mars days than ones of 669.

Rodolfo

P.S. As there is a disparity of numbers. So why not celebrate the birth party for two days starting from the sol 668 and ends the sol 670.

Your numbers are off slightly. See Mars 24 FAQ and Wikipedia Mars Timekeeping page and NASA Mars facts page

It's 686.9726 earth days (solar days of precisely 24 hours) for the Martian tropical year and 668.5921 martian solar days or as we've come to know and love, sols.

A Martian Sol is 1.027491 Earth solar days and the Tropical year is 686.9726 earth solar days.

The MArs 24 notes are well worth a read.

Thank you much for the reference. I had trouble to decode the sols after reading the JPEG's filenames position 3 to 11 (spacecraft clock) and the help of these number I was able to get the right sols with a MS Excel.

Rodolfo

Excellent idea, Doug. You are an able ambassador for the space enthusiast community.

The west-coast-bound-card has arrived, Shardon Laubach (MER Engineer who worked on auto-nav algos etc) emailed to let me know.

The real question is..can the Science team hold out till the actual birthday before opening the card

Doug

That was a cute idea djellison, im all for it.

Official recognition

http://www.jpl.nasa.gov/missions/mer/flightdir.cfm

Well done