Ground Based Observatory (GBO)

THEMIS Overview

THEMIS (Time History of Events and Macroscale Interactions during Substorms) is part of the NASA Medium-class Explorer (MIDEX) program and should be launched in late 2006 or early 2007. THEMIS is a five-satellite mission with the job of determining the causes of the global reconfigurations of the Earth's magnetosphere that are evidenced in auroral activity. THEMIS consists of 5 small satellites, carrying identical suites of electric, magnetic, and particle detectors, that will be put in carefully coordinated orbits. Every four days the satellites will line up along the Earth's magnetic tail, allowing them to track disturbances. The satellite data will be combined with observations of the aurora from a network of observatories across the Arctic Circle in Canada and Alaska. Teams at the University of Berkeley and the University of Calgary are responsible for building and deploying the ground based array of observatories.

Each ground based observatory (GBO) will consist of an all sky camera and a magnetometer connected to rack of equipment called the Observatory Support Electronics (OSE). As well, a host of support equipment such as a computer, a GPS antenna, and a satellite dish (in the event that an internet connection is not available at the site) will be deployed at each site.

GBO Site Requirements

The minimum site requirements for a GBO are listed below:

If available we would also like to make use of an existing internet connection. If not, then we would like to deploy a small Infosat Satellite dish for real time recovery of the data. This of course increases the "footprint" of our equipment on the site, and slightly increases our power requirements.

As well, if available, we would like to utilize an existing building or similar infrastructure in which would could place the OSE component of the GBO equipment and on which we could mount the ASI housing and a GPS antenna (see above). If this is not available we can deploy the rack of equipment outside in a custom built environmental enclosure.

The GBOs will be an active part of the THEMIS program from 2005 to 2010.

GBO Components

Observatory Support Electronics (OSE)

The brains of a THEMIS GBO are contained in a shock mounted shipping case (picture below). This rack of electronics will ideally be placed inside an existing structure and the cables from the OSE will be run outside to the instruments. If this is not possible that the OSE can be deployed outdoors contained in a custom made environmental enclosure (the Computer System Enclosure, CSE) (coming soon!!). The OSE is 25"x28"x29" and wieghs roughly 130 pounds. "

THEMIS Observatory Support Electronics (OSE)

Computer System Enclosure (CSE)

The CSE weighs roughly 60 pounds.

THEMIS Computer System Enclosure (CSE)

All Sky Imager (ASI)

The THEMIS all sky imager (ASI) is contained inside an temperature controlled environmental enclosure (pictured below). The enclosure is 21" long by 9" diameter and wieghs about 30 lbs.

THEMIS ASI Enclosure.

The ASI can currently be mounted to a pole or to a horizontal surface, but custom mounting brackets can be used for installations in other circumstances. The ASI is connected to the OSE with two 30 foot long cables.

Magnetometer (GMAG)

At several sites a magnetometer (GMAG) will be also be deployed. The GMAG will be ideally be buried in the ground 100 feet from the OSE in an area of low magnetic interference. The black tube is is 21" long by 5" in diameter. The cable that connects the GMAG to the OSE will be encased in a garden hose for protection from the elements and wildlife. This cable will need be layed in a shallow trench.

THEMIS Magnetometer

Global Positioning System (GPS)

The THEMIS GBO's will use GPS to accurately determine the time at each site. A standard commercial GPS antenna (picture below) will be deployed adjacent to the ASI.

GPS Antenna

Satellite Dish

Each THEMIS GBO will be connected to the internet to facilitate site monitoring and data retrieval. If an existing internet connection is not available then a satellite dish will also be installed at the GBO site. The size of the dish will depend on the latitude of the site. An example dish is picture below.

Infosat 1.2 meter Dish.

Custodial Duties

Each THEMIS site will have a local custodian who has easy access to the GBO, particularly during the winter months when the long nights make conditions ideal for auroral observation. The custodian will be responsible for the routine maintenance and upkeep of the observatory, including periodic removal of snow from the dome and satellite dish, removal and shipment to the University of Calgary of data disk and occasionally some minor trouble shooting.