SI: metre Mystery Cache

The International System of Units (SI), commonly known as the metric system, is the international standard for measurement. The SI plays an essential role in international commerce and is commonly used in scientific and technological research and development. This cache is part of the SI geoart that allows you to learn about the SI units. Visit the introduction cache to learn more about this geoart.

Length: metre (m)

The metre is the SI base unit of length. Historically, 1 metre was defined as one ten-millionth of the distance from the equator to the North Pole. In 1889, the International Bureau of Weights and Measures (BIPM) created the international prototype metre. The length of this prototype bar defined the metre until 1983.

Thirty platinum-iridium alloy bars were casted. No.6 was selected as the international prototype, while others were calibrated against the international prototype, and distributed to the signatory nations of the Metre Convention for use as national standards. United States received No.27, shown in the picture below:

In 1983, the metre was once again redefined. Its current definition is: the metre is the length of the path travelled by light in vacuum during a time interval of 1/299792458 of a second.

This Geocache

What’s the minimum distance between two traditional geocaches in metres? Add 443 to this number to get ABC.

NASA launched an asteroid study and sample-return mission on 8 September 2016. On 15 April 2020, the spacecraft performed the first sample collection rehearsal. During the exercise, what’s the distance from surface, in metres, of performing the back-away burn? Add 366 to this number to get DEF.

Final coordinates: N 39° 07.ABC W 077° 09.DEF

You can validate your puzzle solution with certitude.

Cache container is a baby-nano with tiny log sheet. A pair of tweezers is mandatory for log retrieval. To conserve space, please omit the date and write the first two letters of your username only.

Some hides are located along a road without sidewalk. For your safety, please walk on the grass out of the car lanes, and avoid going at night without wearing a safety vest.

Lists of Caches in SI geoart

0. introduction
1. second and hertz
2. metre
3. kilogram
4. m/s and km/h
5. mole
6. radian and steradian
7. m/s² and newton
8. m² and pascal
9. joule and watt
10. ampere and coulomb
11. volt and farad
12. ohm
13. kelvin
14. candela, lumen, and lux
15. bushel
16. foreword & afterword
17. prize distribution