IVM Starts Final Functional and Environmental Testing

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The first of two IVMs, which is designated IVM-A based on its location on the spacecraft (facing forward), started End Item Testing (EIT) this week. The EIT is a thorough functional checkout including calibration over temperature and serves as the entry point baseline for environmental testing. Environmental testing will include EMI/EMC, Vibration and Thermal Vacuum testing which simulate the launch and flight environments as closely as possible. Testing will be completed in about eight weeks. 

While the IVM enjoys many years of heritage, the ICON IVM has improvements and modifications that will produce measurements of the plasma drift with unprecedented sensitivity to achieve the ICON science goals. 

The second IVM (IVM-B) fabrication is following closely behind IVM-A and is in the final phases of test and assembly. IVM-B faces in the aft direction on the spacecraft during normal operations, when the remote sensing optical instruments view the northern hemisphere. However, it will be activated during operations when the spacecraft is rotated to allow the optical instruments to view the southern hemisphere.

FUV Ships to Belgium for Alignment, Environmental Tests and Calibration in the Far Ultra Violet

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The preliminary alignment for the Far Ultraviolet Spectrograph (FUV) instrument using visible wavelength light has been completed at Lockheed Martin. The next phase of testing will see the instrument ship to Belgium to complete the alignment in the FUV in a specialized vacuum chamber.

The FUV ICON instrument has an articulating field of view. In order to accommodate this, special machinery is required to rotate the instrument during alignment, testing and calibration while inside the vacuum chamber. Centre Spatial de Liege (CSL) in Belgium will provide this unique ultraviolet vacuum facility.

The design for the FUV instrument is such that the optical system can be focused using visible light and a visible grating, as well as FUV light and grating. This is preferable, since alignment using UV must be performed in a vacuum chamber, which makes it more challenging to conduct the alignment.

Over the past four weeks, the SSL team has been traveling to Lockheed Martin where the instruments’ mirrors were carefully adjusted to achieve best focus and optimum spectral performance at visible wavelengths. The visible wavelengths chosen were suitably scaled to simulate performance at the FUV operating wavelength.

The next phase of testing will see the optics package ship to Centre Spatial de Liege (CSL) in Belgium. After verifying the visible alignments were maintained, and no shifts happened during transport, the UV grating and the two UV cameras will be installed and UV alignment will begin.

The MIGHTI Engineering Unit optics integration and vibration test is complete

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ICON’s Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument includes two identical optical assemblies, one for each of the perpendicular fields of view that will observe thermospheric wind-vector and temperature profiles. An engineering unit of the optical assembly was completed and successfully vibration tested in June 2015 at the Naval Research Laboratory.

EUV Alignment and Calibration has begun

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ICON's Extreme Ultraviolet (EUV) instrument is an “imaging spectrometer”. Its 2 dimensional detector records spectral information over the range 58.4 to 83.4 nm in the one direction, and records 12 degree wide x 1/4 degree high slices of the sky over a 16 degree field of view in the other direction.

In preparation for alignment of the toroidal grating used in the EUV instrument, an optical system has been setup to simulate the cylindrical wavefront. This simulates the instrument’s view for each slice of sky while in orbit. The optical set up consists of a convex sphere and a concave toroid that produces a line image on the EUV entrance slit to simulate what EUV will observe in space. This optics pair will be used to first align the EUV instrument using visible light, then the final alignment will take place in a vacuum chamber using EUV radiation, since EUV light is not transmitted in air.

ICON passes Critical Design Review

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During the review, each instrument and system were reviewed, and plans for integration of these systems onto a unified payload finalized. The team was successful in demonstrating their ability to complete these tasks on schedule. All instruments will be delivered to Utah for integration by the end of the calendar year, before delivery to Orbital ATK in Virginia by May 2016, in preparation for launch in June 2017.

Project Manager Bill Craig said “One of the key strengths was the consistency of the team; we were compared to the high quality expected of a Class B mission; a standard we set for ourself at PDR” and P.I. Thomas Immel complemented the team on an outstanding job in preparing and delivering a very successful review.

Congratulations to the entire ICON team… Onwards to Integration!

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ICON skin is based on Greytness by Adammer
Background image, courtesy of NASA, is a derivitave of photograph taken by D. Pettit from the ISS, used under Creative Commons license