The Alvin data system provides real time data acquisition,
logging, display and general computing. A list of the data items
normally available for logging or display is provided in Appendix
A. Displayed data is viewed on the Alvin video system
as data overlays on video images.
The major “product” of the data system is the data stored on the computer’s hard disk. After each dive this data is transferred to the user in one of several different ways. The normal media is 4.7GB DVD-Rs. File transfer from the shipboard network via Ethernet is also available; guest computers should be network-tested in advance and users should be prepared to reconfigure network parameters in order to access the shipboard net. Users must contact the Alvin Group prior to a cruise if the estimate of data storage requirements (as described above) exceeds 1MB per dive.
More detailed information on the data system is provided in the Scientific Equipment Interface section.
Digital cameras have been purchased for general use by scientists using Alvin on R/V Atlantis. These cameras have been gas-tested and are approved for use in the Alvin sphere. Digital camera technology continues to improve, and new features are being added to make these cameras more appropriate for use in Alvin. As new products become available, they will be made available to Alvinusers. The characteristics of onboard digital cameras are shown in the accompanying table.
|Make/Model||Canon G2||Nikon D1||Canon G7|
|Zoom||34-102mm macro||52-105mm macro||34-102mm macro 3X|
|File Format||JPEG/Canon RAW||TIFF/JPEG||JPEG/Canon RAW|
|Max size (MB)||2.0/2.9||7.8/1.3||2.9|
|Media Type||ATA I,II||ATA I,II||ATA I,II|
These cameras allow the observers to take pictures through Alvin’s viewports of seafloor features and animals or processes of interest during the dive. They are most useful for documenting sampling or instrument sites in order to aid post-dive debriefing and planning for subsequent dives, as well as providing images suitable for onboard web site preparation.
Investigators may also use their own cameras. If flash photography is desired, the camera must be equipped with a hot shoe to accommodate the remote trigger device. To prevent scratching of the viewports, the lens ring on all cameras must be taped or otherwise isolated by a soft material.
Several important points should be noted by potential users:
- Do not put the lens up to the viewport. The viewports are plastic and can be easily scratched; hold the lens so that it is just off the viewport surface.
- Familiarize yourself with the camera functions prior to the dive -- groping around in the dark for the instructions or trying to figure out the button settings on each camera is not an efficient way to spend your dive time.
- Pictures can be taken out the front or side viewports using the HMI lights. The cameras can also be synched to the external strobes via the infrared sending units connected to cameras equipped with a hotshoe. For the digital cameras there are several buttons that have to be pushed in order to override the automatic settings; please consult the camera manual onboard. Also check with the Alvin Expedition Leader for details of flash use.
- Shooting tips -- since lighting for the hand-held cameras is provided by external strobes, shutter speed does not control exposure. Bear in mind that shutter speed must be within the strobe sync range, which is usually 1/125 second or slower. 1/60 second works well. These settings are also applicable to digital cameras while in the manual mode.
Recommended settings are as follows:
- Shutter speed: 1/60 sec.
- Aperture: 400 ASA equivalent: 1-3 meters = f4; 3-5 meters = f2.8; <1 meter="f5.6" to f8
- 200 ASA equivalent: 1-3 meters = f2.8; 3-5 meters = f2; <1 meter="f4" to f5.6
- Focus distance: 7 ft. (2 meters)
- Minimum time between pictures (for strobe recharge): 5 seconds
The viewports exhibit the least distortion when viewing directly out the centerline. So for best photographs, keep the camera pointed as directly out the viewport as possible (perpendicular to the viewport surface). This is also the area illuminated by the strobe and viewing lights.
It is advised that you set the focus distance at 7 ft. (2 meters) when the sub is moving since it is hard to focus as the terrain moves by. When the sub is stationary you can then focus on a particular subject. Telephoto lenses have very little depth of field and are very difficult to focus in the low light levels typical to this environment.
If time permits, external viewing lights should be turned off after focusing. With the slow shutter speeds the external lights will reduce the contrast of the picture.
- Downloading images -- several options are available for downloading the images either directly from the cameras via cables onboard (see SSSG tech) or Flashcard media readers (see SSSG tech and onboard crib sheets). You should be sure to bring sufficient storage media (CD-ROMs or DVD-Rs) as each of the highest quality images can be multi-MB in size.
- Camera care -- please remember that these cameras are for use by all scientists onboard and that investigators joining the ship after your cruise are also planning on using them. If there are problems with the cameras please let the Alvin Expedition Leader or SSSG Tech know immediately so they can be remedied. Please take good care of them during your cruise so they can continue to provide this capability for all science users.
Hand-held video camera
A hand-held digital camcorder (Sony DSR-PD100A as of June 2001) is available for use by the observers for shooting through the viewports. Its effective range extends approximately 2 meters beyond the viewport. Lighting is supplied by external viewing lights. Digital tape is not provided for this hand-held camcorder and tapes made with this system will not be archived. Only Sony DVM-60PR2 miniDV tapes are suitable for use in this camera.
Operation of the camera will be explained during orientation or on request. It is suggested that observers practice with the camera the evening before their dive to ensure familiarity with the controls.
Basic basket Fibergrate platform
Basket load calculation diagram
Basket frame loaded with sampling devices
A generic 1.5" tubular pipe frame is fitted to the front of the submersible to accomodate science tools, equipment and collected samples. A fiberglass grate, 36" wide by 48" long serves as the base platform, to which an assortment of dive-specific equipment can be attached. Instruments are then either bolted through or haose clamped to the grate. Devices to be deployed or recovered as part of the dive evolution should be supplied with a holster or quiver that will secure the device (without the aid of one of the submerisble's manipulators) during sub launch and recovery.
The science basket assembly must be jettisonable in the event of entanglement, bottom fouling or if added buoyancy is needed for any reason. Accordingly, all equipment attached to the basket must have the ability to be released with the basket. Alvin Operations provides disconnect "boots" for any electrical connections to the submersible, which will pull apart and disengage in the event of a basket release.
The jettison requirement also limits the maximum load that can be carried in the basket because of limitations in the release mechanism. This load limit is 400 lbs water weight as measured at the basket release. The scale diagram at left allows investigators and Alvin personnel to calculate basket load using the following formula with two variables: equipment weight and distance from a known point on the submersible:
In other words, the sum of all weight/distance products for items to be carried in the basket must be less than 20,000 in-lbs. The limit of 20,000 is derived from the maximum of 400 lbs at the basket release times 50 inches, the distance from the reference point. Using the formula, investigators can design basket loads for a particular dive. The Alvin Expedition Leader has ultimate authority over the final configuration of any basket load.
Special basket configurations and frames for dive-specific equipment or projects can be constructed with advanced notice.
Portable audio cassette tape recorders with cassettes are carried on each dive for scientists’ use. Users are also encouraged to bring personal tape recorders for replay/debriefing purposes. Tapes recorded during each dive remain with the user and copies are not archived. Also, an in-hull open microphone provides a voice log on the audio track of the primary video tape, which normally runs for the duration of the “on-bottom” time.
The Alvin video system consists of three principal subsystems:
video sources, recorders, and monitors with source selection
switches. See the Science
Equipment Interfaces section for a detailed description
of the system components.
During the 2001 overhaul period Alvin switched from analog HI-8mm video tape recording format to the Sony DVCam Professional format. The tapes used are Sony PDV-124N (124 minute duration). In order to provide high quality images for both the scientists and the archives there will be no data routinely burned as overlays onto the tapes as they are recorded during a dive. Overlay data will be available on the observer displays during dives and may be burned onto the original recording if specifically requested. A time stamp and some dive data will be recorded onto the ancillary data packet field of the tapes. The time stamp will be visible on the tape deck display during playback, but the extra data will not be visible without additional hardware as described below.
One copy of the original tapes will be made in the Alvin duplication rack on Atlantis and turned over to the Chief Scientist. Originals are sent to WHOI as required by the Deep Submergence Facility Archive Policy. The copy will be a clone (an exact copy made without decompressing and recompressing the data and therefore without degradation of original quality). The clone tapes will be DVCam Pro format and can be further cloned or copied in the science duplication rack by the science team (see the PDF document on Video Duplication for additional information below). At the science duplicating station digital tapes (DVCam or MiniDV from the sphere camcorder) can be cloned or copied to DVCam/MiniDV tapes and also copied to VHS, SVHS or DVD-R media. During this process a pre-defined data set can be burned into the copies as an overlay if desired. The science program must provide all media associated with use of this duplicating station.
Underwater lights are located outside the viewports. Each observer viewport has one or more lamps positioned to illuminate viewing areas. The observer viewport lights are individually controlled by switches near the viewports and by the pilot’s master control switches. Additional lighting can be supplied if necessary but the effect on the power budget must be carefully considered. Forward illumination is provided by a combination of several HMI lamps. A 400 watt thallium iodide (TI) arc lamp can be fitted in place of one of the 400 watt HMI lamps if desired.