VOLUME I Multinational Maritime Tactical Instructions and Procedures

(2) Active or passive sonar, MAD, radar, ESM, EER, active or passive sonobuoys, towed acoustic
arrays, and other devices; such contacts are investigated or tracked, without confirming all of the characteristics
listed for PROBSUB, but are suspected to be of submarine origin.
(3) Surface flares, blinker lights, tracer lights, and similar indications are thoroughly investigated,
do not lead to submarine sightings or sensor contact, but are suspected to be of submarine origin.
(4) Surface ship HF/DF contact on a signal classified as being of submarine origin.
d. Confidence Level. The classification POSSUB must always be amplified by adding an assessment
of the confidence level. Confidence levels are specified as follows:
(1) LOW CONFIDENCE — A contact that cannot be regarded as NONSUB and requires further investigation.
This assessment may be further amplified by using grades 1 and 2, 1 being the lower grade.
(2) HIGH CONFIDENCE — A contact that from the evidence is firmly believed to be a submarine,
but it does not meet the criteria established for PROBSUB. This assessment may be further amplified by
using grades 3 and 4, 3 being the lower grade.
e. NONSUB (Nonsubmarine Contact). After investigation, a contact that is shown to have
characteristics that exclude the possibility that it is a submarine. NONSUB is a firm statement that the classifier
is entirely satisfied his contact is not a submarine. When a contact is lost which was previously classified
POSSUB or PROBSUB, it is dangerous and wrong to amend the classification to NONSUB without
the most thorough investigation.
9203 CONTACT REPORTING
a. General Considerations.
(1) Initial Contact Reporting and Classification. To initiate rapid response to counter what
may be an imminent enemy attack, the initial contact (whether classified or not) must be reported immediately.
When not included in the initial report, a classification must be made in the subsequent amplifying
report. Where possible, contacts should additionally be amplified by propulsion and class.
NOT RELEASABLE
(2) Subsequent Evaluation. Reclassification of a contact continues throughout the entire ASW
action, and subsequent reports by a unit may amend or amplify the classification. Prosecuting units must
continually review contact classification using other sensors as available.
(3) Command Responsibility. When more than one ASW unit is in contact, the SAC or OTC
(or ASWC if delegated) evaluates all information and classifications and reports the contact together
with his classification.
(4) NOT RELEASABLE
MTP 1(D), Vol. I
(5) Contact Information. The method in which contact was obtained, maintained, or localized
may be of assistance in assessing a passive acoustic contact report.
NOT RELEASABLE
9-21 CHANGE 2