"As the sensors associated with the various surveillance missions improve, the data volumes are increasing with a projection that sensor data volume could potentially increase to the level of Yottabytes (10^24 Bytes) by 2015."
Note the qualifiers and the future time date; also, this is talking about raw sensor data. It is not uncommon for raw data to be reduced by a few orders of magnitude via aggregation, compression, and simply discarding irrelevant sensor readings before hitting permanent storage (e.g. look at the LHC).
"As the sensors associated with the various surveillance missions improve, the data volumes are increasing with a projection that sensor data volume could potentially increase to the level of Yottabytes (10^24 Bytes) by 2015."
Note the qualifiers and the future time date; also, this is talking about raw sensor data. It is not uncommon for raw data to be reduced by a few orders of magnitude via aggregation, compression, and simply discarding irrelevant sensor readings before hitting permanent storage (e.g. look at the LHC).