Photo proof of good progress on IKAROS sail deployment

Posted By Emily Lakdawalla

2010/05/31 04:00 CDT

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The images below are self-portraits by IKAROS. While I think it is automatically cool for spacecraft to take photos of themselves in places far beyond Earth, they usually do so for a purpose other than vanity. In this particular case, they're photo proof that the multi-step process of the deployment of IKAROS' square solar sail is going according to plan! I took them from this JAXA site (hat tip to "Punkboi" for pointing out the update).

ISAS / JAXA

IKAROS tip mass deployed (Cam 1)

What exactly are we looking at? First, here's an explainer from the IKAROS press kit that shows the steps involved in the deployment process. I believe -- but am not certain -- that the photos above document the successful completion of the second step in the top row. My reasons for that have to do with the helpful spacecraft diagrams that JAXA posted along with the camera images (see below). If I have correctly interpreted the Google translation of the JAXA update, the sail monitoring camera images were taken on May 28.

ISAS / JAXA

IKAROS sail deployment diagram

Here are a couple more images from the JAXA update that help to document what we're seeing. First, a photo of the spacecraft showing the relative positions of tip masses (blue text) and cameras (red):

ISAS / JAXA

IKAROS with tip masses and cameras labeled

A photo of the cylindrical IKAROS spacecraft during assembly is labeled with the location of one of four deployment monitoring cameras (red text) and two of four "tip masses," half-kilogram weights that will assist in the deployment of IKAROS' square sail. The tip masses are attached to the sail's four corners. A rolling stopper (black vertical bar across the folded sail) will control the rate of deployment of the sail by the tip masses.

And here's a diagram illustrating what the cameras should see once the tip masses are deployed. Cameras are marked by red text with their fields of view in blue; the orange text marks the location of a tip mass after it's deployed.

ISAS / JAXA

Drawing of the IKAROS sail monitoring cameras' field of view

IKAROS is equipped with four wide field-of-view cameras to monitor the deployment of its sail. In this diagram, the field of views of the cameras are shaded in blue. The "tip masses" that support the sail's deployment are located in between the cameras. After the tip masses are released from the spacecraft, they remain tethered and rotate with the spacecraft, but lag in their rotation on their flexible tethers, causing each one to appear within the field of view of one camera.

The press kit explainer states that the tip mass deployment happened while the spacecraft was rotating at 2 rotations per minute (rpm). According to IKAROS' Twitter feed, the spacecraft is now up to 25 rpm; that must mean they're proceeding with the steps leading to "first stage deployment," in which the still-fan-folded sails will be dragged outward by the tip masses. I'm looking forward to pictures of that!