MODIS Direct Broadcast
NASA/GSFC Ground Receiving Station

About MODIS Direct Broadcast
MODIS is one of the five instruments on the Terra spacecraft. One of the unique features of the MODIS instrument is its Direct Broadcast capability. Generally, spacecraft collect data and then store it on board until it passes over a ground station set up to receive the data, at which point it transmits the data in one large batch. This avoids losing data taken when the spacecraft is out of sight of any ground stations, such as when it is over the ocean.

MODIS does store data on board for later download, but it also broadcasts the raw data it collects immediately, on the chance that someone on the ground below is listening. This is called Direct Broadcast of the data. NASA/GSFC has the antennas and other equipment necessary to receive and process MODIS Direct Broadcast data whenever the spacecraft is above the horizon. The Overpass Predictor can be used to determine when there will be a Terra spacecraft overpass of NASA/GSFC (Greenbelt, MD) or any other location that may have a Modis Direct Broadcast receiving station.

About the Direct Broadcast images
The MODIS instrument takes data by scanning from side to side as it passes over the earth. The instrument points straight down, and "sees" up to 55 degrees to either side. Because of this, the image is most accurate down the centerline of the image, and becomes more distorted (compressed) towards either side. This is a combination of the angle MODIS is viewing the ground at and the curvature of the Earth.

The images are built from MODIS bands 1 (red), 4 (green) and 3 (blue). The "small" image below has a resolution of 3 kilometers per pixel at nadir (the picture's centerline). A larger version of the image with 1 kilometer per pixel resolution at nadir is available - it's about 1 MB in size and is 1354 pixels wide. The height depends on the length of the overpass, but generally exceeds 3600 pixels.

Earlier MODIS DB Images

12 Nov 2001	1704 UTC	small (88 kb)	large (1542 kb)
12 Nov 2001	1526 UTC	small (147 kb)	large (2555 kb)
09 Nov 2001	1634 UTC	small (78 kb)	large (1331 kb)
08 Nov 2001	1729 UTC	small (48 kb)	large (797 kb)
08 Nov 2001	1550 UTC	small (117 kb)	large (1945 kb)
07 Nov 2001	1646 UTC	small (89 kb)	large (1495 kb)
07 Nov 2001	1508 UTC	small (126 kb)	large (2154 kb)
06 Nov 2001	1742 UTC	small (51 kb)	large (860 kb)
05 Nov 2001	1520 UTC	small (121 kb)	large (1933 kb)
02 Nov 2001	1629 UTC	small (106 kb)	large (1741 kb)
02 Nov 2001	1450 UTC	small (106 kb)	large (1726 kb)
01 Nov 2001	1722 UTC	small (89 kb)	large (1442 kb)
01 Nov 2001	1544 UTC	small (94 kb)	large (1472 kb)
31 Oct 2001	1648 UTC	small (4 kb)	large (49 kb)
31 Oct 2001	1502 UTC	small (19 kb)	large (319 kb)
30 Oct 2001	1735 UTC	small (49 kb)	large (729 kb)
29 Oct 2001	1652 UTC	small (90 kb)	large (1568 kb)
26 Oct 2001	1802 UTC	small (33 kb)	large (563 kb)
26 Oct 2001	1622 UTC	small (114 kb)	large (1845 kb)
26 Oct 2001	1445 UTC	small (93 kb)	large (1412 kb)

Credits
Real-time directly broadcasted MODIS data is being provided by the Code 935 Direct Readout Laboratory at the Goddard Space Flight Center.
Email contact: patrick.coronado@gsfc.nasa.gov