JUNO Earth Flyby - Pictures

3-band color pictures

Like previous MSSS cameras (e.g., Mars Reconnaissance Orbiter’s Mars Color Imager) Junocam is a "pushframe" imager. The detector has multiple filter strips, each with a different bandpass, bonded directly to its photoactive surface. Each strip extends the entire width of the detector, but only a fraction of its height; Junocam's filter strips are 1600 pixels wide and about 155 rows high. The filter strips are scanned across the target by spacecraft rotation. At the nominal spin rate of 2 RPM, frames are acquired about every 400 milliseconds. Junocam has four filters: three visible (red/green/blue) and a narrowband "methane" filter centered at about 890 nm.

The spacecraft spin rate would cause more than a pixel's worth of image blurring for exposures longer than about 3.2 milliseconds. For the illumination conditions at Jupiter such short exposures would result in unacceptably low SNR, so the camera provides Time-Delayed-Integration (TDI). TDI vertically shifts the image one row each 3.2 milliseconds over the course of the exposure, cancelling the scene motion induced by rotation. Up to about 100 TDI steps can be used for the orbital timing case while still maintaining the needed frame rate for frame-to-frame overlap. For Earth Flyby the light levels are high enough that TDI is not needed except for the methane band and for nightside imaging.

Image Information	Raw Image	Red Image	Green Image	Blue Image	Full-Color Image
Image Information	(click for a full-sized image)
Image 1: Moon color Time: 04:07:00 PDT Exposure: 0.9 milliseconds Time delay integration: 1
Image 4: Earth dayside Time: 11:54:30 PDT Exposure: 0.2 milliseconds Time delay integration: 1
Image 6: Earth dayside Time: 11:59:00 PDT Exposure: 0.1 ms Time delay integration: 1
Image 8: Earth dayside Time: 12:03:30 PDT Exposure: 0.2 ms Time delay integration: 1
Image 10: Earth dayside Time: 12:08:00 PDT Exposure: 0.3 ms Time delay integration: 1
Image 12: Earth dayside Time: 12:12:30 PDT Exposure: 0.3 ms Time delay integration: 1

1-band imaging

Methane-filter images will also be taken during Earth flyby. The methane filter detects near-infrared light which is strongly absorbed by methane. At Jupiter, the methane band will be used to detect atmospheric regions with the highest concentrations of methane, which can be used to vertically probe atmospheric structure. On the other hand, Earth's atmosphere does not contain enough methane to heavily affect the methane-band images. What is noteworthy is that chlorophyll (the pigment present in plants that gives them their green color) reflects the color of light picked up by the methane band very well; so instead of detecting methane, the methane band will highlight areas of dense vegetation, cloud cover permitting. In addition, since the methane filter allows significantly less light to pass through than the visible light bands, it will be better-suited to take photographs of the Earth (which is very bright compared to Jupiter due to its proximity to the Sun) than the color bands, as the simimages taken by the color bands may be too saturated to see clearly.

In addition to the methane images, a few simimages will also be taken in exclusively one visible color (red, green, or blue).

Image Description	Raw Image	Processed Image
Image Description	(click for a full-sized image!)
Image 2: Moon Band: Methane Time: 04:09:00 PDT Exposure: 3.2 ms Time delay integration: 3
Image 3: Jupiter Band: Green Time: 11:51:30 PDT Exposure: 3.2 ms Time delay integration: 60
Image 5: Earth dayside Band: Methane Time: 11:57:30 PDT Exposure: 3.2 ms Time delay integration: 3
Image 7: Earth dayside Band: Methane Time: 12:02:00 PDT Exposure: 3.2 ms Time delay integration: 3
Image 9: Earth dayside Band: Methane Time: 12:06:30 PDT Exposure: 3.2 ms Time delay integration: 3
Image 11: Earth dayside Band: Methane Time: 12:11:00 PDT Exposure: 3.2 ms Time delay integration: 3
Image 13: Earth dayside Band: Methane Time: 12:15:30 PDT Exposure: 3.2 ms Time delay integration: 6
Image 14: Earth nightside Time: 12:12:30 PDT Band: Red Exposure: 3.2 ms Time delay integration: 60
Image 15: Earth nightside Time: 12:19:30 PDT Band: Green Exposure: 3.2 ms Time delay integration: 60
Image 16: Earth nightside Band: Blue Time: 12:26:00 PDT Exposure: 3.2 ms Time delay integration: 60
Image 17: Radiation belt passage Band: Red Time: 12:31:00 PDT Exposure: 3.2 ms Time delay integration: 60