Target Corporation, one of America’s largest and best known general merchandise retailers, has added a tasteful and fun element of light to the Minneapolis skyline.

In a colorful light display known as “Target’s Northern Lights”, some 130 Martin Exterior 600 color changers illuminate 40’ light pipes encircling the top two floors of the company’s new world headquarters and retail store in downtown Minneapolis. The original installation consisted of 68 Exterior 600s with light pipe (3M), with 62 more added in early September.

Originally planned to coincide with the opening of Target’s downtown store in October of 2001, the Northern Lights project was pushed forward due to September 11th in order to illuminate the sky with patriotic hues.

Lighting top two floors
The Target headquarters consists of two towers, 14 and 34 stories respectively. A curtain wall on the main tower’s top two floors lines the perimeter of the building’s large penthouse. In the gap between the penthouse and the curtain wall (12 meters high by 2 meters deep), mounted behind frosted glass, are 130 Martin Exterior 600 color changers each with a 40’ light pipe attachment. The Exterior 600s allow for a limitless palette of color changes, as well as fades and dramatic effects like quick color sequencing and strobe.

Using light pipe from the 3M company and exterior color changers from Martin, 3M technical specialist Steve Pojar was instrumental in creating the Northern Lights effect. “The original plan was to light the area behind the curtain wall with metal halide lamps, creating a soft white glow,” states Steve, “but Target had more creative ideas, namely to add an Aurora Borealis effect to the Minneapolis skyline.”
 
Target requested a concept from 3M on how to achieve a visible yet subtle Northern Lights look while insisting on an energy efficient, easy to maintain and cost effective solution.

Steve designed a scale model of a section of the space by using 3M light pipe technology to create a soft glow on the curtain wall by placing a halogen lamp on each end of the vertically oriented light pipes, a blue filter on the top lamps and green on the bottom. The colors were chosen based on Steve’s own personal experience viewing the Northern Lights phenomenon. Using a DMX dimmer pack, the green color could be controlled to fade and move across the facade.

More color
But the Aurora Borealis evokes different images to different people. The challenge lie in determining what the customer expects. “Everyone has a different view of what the Aurora Borealis looks like,” states Steve. “The green and blue were not felt to be colorful enough, so I replaced the green lamps with small color changers.”

That was a hit with Target. The next step was then to produce a mock-up of the building.  For this Steve used 10-meter light pipes lighted by halogen lamps with scrollers. The architects and Target personnel liked the uniformity and softness delivered by the light pipe. The next step was selecting an appropriate color changer for the application. 

Exterior 600
Steve looked for an outdoor fixture with full color mixing and dimming. The fixture also needed to incorporate a long life lamp. (Although the space is sheltered from rain and snow, the air in the space is not conditioned, so an outdoor fixture was required.)

Steve comments on the fixture choice. “I looked at several different brands and selected the Martin Exterior 600 because of its compact size, the fact that it had been used in similar climates like Chicago, and because Martin was quick to respond and willing to help. Jim Fuller (Martin US Architectural Segment Manager) was willing to help out with the demonstrations, provide loaner fixtures, and come to Minnesota in the winter!  We spent a few cold evenings on that building.”

The space is also the air intake plenum for the building so combustible materials such as standard plastic light pipes could not be used.  To meet the building codes Steve had to enclose the 3M films in glass pipes and seal the pipes to the Exterior 600 fixtures. “I made use of 3M´s engineering department to design a suitable interface and hanging system for the light pipes and for the Martin fixtures. The 130 exterior/light pipes are actually suspended from the roof, rather than mounted to the interior wall, and are spaced evenly about 3 meters apart.”

Lighting control of the luminaires is handled through a PC-based control system, the Martin LightJockey, which allows each light pipe to be individually controlled. The system has been turned over to Target´s advertising and marketing department.